Distance Midpoints in the Complex Plane
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Algebra 2 › Distance Midpoints in the Complex Plane
Complex numbers correspond to points $(a,b)$ in the plane. Using the midpoint formula $\dfrac{z_1+z_2}{2}=\dfrac{a+c}{2}+\dfrac{b+d}{2}i$, find the midpoint of the segment from $z_1=7-3i$ to $z_2=-1+5i$.
$3+i$
$3-4i$
$6+2i$
$8+2i$
Explanation
This question tests your understanding of finding midpoints between complex numbers on the complex plane using formulas that mirror 2D coordinate geometry. The midpoint of two complex numbers $z_1 = a + bi$ and $z_2 = c + di$ is $\frac{z_1 + z_2}{2} = \frac{a + c}{2} + \frac{b + d}{2}i$, averaging the real and imaginary parts separately, just like in coordinate geometry! To find the midpoint from $7 - 3i$ to $-1 + 5i$: (1) Add: $(7 - 3i) + (-1 + 5i) = 6 + 2i$. (2) Divide by 2: $\frac{6 + 2i}{2} = 3 + i$. The midpoint is at $3 + i$—fantastic! Choice A correctly applies the midpoint formula as the average. Choice B adds without dividing: $6 + 2i$ is the sum, not the midpoint—always divide by 2! For a transferable strategy, average reals and imaginaries: midpoint of $2 + 4i$ and $6 - 2i$ is $\frac{2+6}{2} + \frac{4-2}{2} i = 4 + i$, simple as that. You're progressing wonderfully—keep practicing!
Complex numbers can be viewed as points $(a,b)$ on the complex plane. The midpoint of the segment from $z_1=a+bi$ to $z_2=c+di$ is $$\frac{z_1+z_2}{2}=\frac{a+c}{2}+\frac{b+d}{2}i$$ which matches the coordinate midpoint formula. What is the midpoint of the segment from $z_1=4-i$ to $z_2=2+5i$?
$3-3i$
$6+4i$
$1+2i$
$3+2i$
Explanation
This question tests your understanding of finding midpoints between complex numbers on the complex plane using formulas that mirror 2D coordinate geometry. The midpoint of two complex numbers $z_1 = a + bi$ and $z_2 = c + di$ is $(z_1 + z_2)/2 = ((a + c)/2) + ((b + d)/2)i$, averaging the real and imaginary parts separately, just like in coordinate geometry! To find the midpoint from $4 - i$ to $2 + 5i$: (1) Add: $(4 - i) + (2 + 5i) = 6 + 4i$. (2) Divide by 2: $(6 + 4i)/2 = 3 + 2i$. The midpoint is at $3 + 2i$, right in the center of the line segment—excellent work! Choice A correctly applies the midpoint formula as the average of the two complex numbers. Choice B adds without dividing: $6 + 4i$ is the sum, not the average—remember to divide by 2 to find the midpoint! For a transferable strategy, add the two complex numbers and divide by 2: for example, midpoint of $1 + 3i$ and $5 - i$ is $(1 + 5)/2 + (3 - 1)/2 i = 3 + i$, averaging coordinates like in geometry. You're building strong skills here—keep going, and complex plane problems will feel intuitive!
Points $z_1$ and $z_2$ on the complex plane form a line segment. The midpoint is $\dfrac{z_1+z_2}{2}$. What complex number is the midpoint of the segment joining $z_1=-6+4i$ and $z_2=2-2i$?
$-2+i$
$-4+2i$
$-2+6i$
$-8+2i$
Explanation
This question tests your understanding of finding midpoints between complex numbers on the complex plane using formulas that mirror 2D coordinate geometry. The midpoint of two complex numbers z₁ = a + bi and z₂ = c + di is (z₁ + z₂)/2 = ((a + c)/2) + ((b + d)/2)i, averaging the real and imaginary parts separately, just like in coordinate geometry! To find the midpoint from -6 + 4i to 2 - 2i: (1) Add: (-6 + 4i) + (2 - 2i) = -4 + 2i. (2) Divide by 2: (-4 + 2i)/2 = -2 + i. The midpoint is at -2 + i, perfectly centered—nice job! Choice A correctly applies the midpoint formula as the average of the two complex numbers. Choice B adds without dividing properly or errs in signs: -4 + 2i is the sum, divide both parts by 2—don't forget the average! For a transferable strategy, add and divide by 2: for example, midpoint of -1 + 2i and 3 - 4i is ( -1+3 )/2 + (2-4)/2 i = 1 - i, just like averaging points. You're doing great— these concepts will click more with practice!
On the complex plane, the point $z=a+bi$ corresponds to $(a,b)$. The distance between $z_1=a+bi$ and $z_2=c+di$ is $|z_1-z_2|=\sqrt{(a-c)^2+(b-d)^2$, the same as the coordinate distance formula. What is the distance between $z_1=3+2i$ and $z_2=1-i$?
$\sqrt{25}$
$\sqrt{13}$
$2+3i$
$\sqrt{5}$
Explanation
This question tests your understanding of finding distances between complex numbers on the complex plane using formulas that mirror 2D coordinate geometry. The distance between two complex numbers z₁ = a + bi and z₂ = c + di is the modulus of their difference: distance = |z₁ - z₂| = √((a - c)² + (b - d)²), which is exactly the 2D distance formula because the complex plane is a coordinate system! To find the distance from 3 + 2i to 1 - i: (1) Calculate difference: (3 + 2i) - (1 - i) = 2 + 3i. (2) Find modulus: |2 + 3i| = √(2² + 3²) = √(4 + 9) = √13. (3) The distance is √13 units—great job applying the formula! Choice C correctly applies the distance formula as the modulus of the difference. Choice B calculates the difference without taking the modulus: 2 + 3i is a vector, not the distance—you must find its length to get the scalar distance! For transferable strategy, always subtract the complex numbers, then take the modulus of the result: for example, distance from 4 + i to 2 - 3i is |(4 + i) - (2 - 3i)| = |2 + 4i| = √(4 + 16) = √20 = 2√5, symmetric regardless of subtraction order. Keep practicing these, and you'll master visualizing complex numbers geometrically—you've got this!
Let $z_1=5+2i$ and $z_2=1-3i$ be points on the complex plane. The distance between them is $|z_1-z_2|=\sqrt{(a-c)^2+(b-d)^2}$. What is the distance from $z_1$ to $z_2$?
$\sqrt{32}$
$4-5i$
$\sqrt{25}$
$\sqrt{41}$
Explanation
This question tests your understanding of finding distances between complex numbers on the complex plane using formulas that mirror 2D coordinate geometry. The distance between two complex numbers z₁ = a + bi and z₂ = c + di is the modulus of their difference: distance = |z₁ - z₂| = √((a - c)² + (b - d)²), which is exactly the 2D distance formula because the complex plane is a coordinate system—these formulas connect complex number arithmetic with geometry beautifully. To find the distance from 5 + 2i to 1 - 3i: (1) Calculate difference: (5 + 2i) - (1 - 3i) = 4 + 5i; (2) Find modulus: |4 + 5i| = √(16 + 25) = √41; (3) Distance is √41 units—geometrically, plot both points and the distance is the straight-line length connecting them! Choice B correctly applies the distance formula as the modulus of the difference. Choice D calculates by just subtracting complex numbers without taking the modulus: the difference 4 + 5i is a vector, not a distance—you must find its length (modulus) to get the distance, so always take the modulus of the difference, don't stop at subtraction! Distance formula for complex numbers: (1) Subtract the complex numbers (order doesn't matter for distance): z₁ - z₂; (2) Find modulus of result: if difference is p + qi, modulus = √(p² + q²); (3) That's the distance—example: distance from 2 - 3i to 5 + i: difference = (2 - 3i) - (5 + i) = -3 - 4i, modulus = √(9 + 16) = 5, and the formula is symmetric—same answer if you subtract in the opposite order. You're making excellent progress—keep visualizing the points to reinforce the concepts!
On the complex plane, let $z_1=1+7i$ and $z_2=5-1i$. Using $|z_1-z_2|$ for distance and $\dfrac{z_1+z_2}{2}$ for midpoint (the same as the coordinate formulas for $(a,b)$ and $(c,d)$), which option correctly gives both the distance and the midpoint?
Distance $=4-8i$, midpoint $=3+3i$
Distance $=\sqrt{80}$, midpoint $=3+3i$
Distance $=\sqrt{64}$, midpoint $=3+4i$
Distance $=\sqrt{80}$, midpoint $=6+6i$
Explanation
This question tests your understanding of finding distances and midpoints between complex numbers on the complex plane using formulas that mirror 2D coordinate geometry. The distance between two complex numbers z₁ = a + bi and z₂ = c + di is the modulus of their difference: distance = |z₁ - z₂| = √((a - c)² + (b - d)²), which is exactly the 2D distance formula because the complex plane is a coordinate system! The midpoint formula also works the same: midpoint = (z₁ + z₂)/2 = ((a + c)/2) + ((b + d)/2)i, averaging the real parts and imaginary parts separately—these formulas connect complex number arithmetic with geometry beautifully. To find the distance from 1 + 7i to 5 - i: (1) Calculate difference: (1 + 7i) - (5 - i) = -4 + 8i; (2) Find modulus: |-4 + 8i| = √(16 + 64) = √80; (3) Distance is √80 units—for the midpoint: (1) Add: (1 + 7i) + (5 - i) = 6 + 6i; (2) Divide by 2: (6 + 6i)/2 = 3 + 3i, exactly halfway between the two points on the complex plane—geometrically, plot both points and the midpoint lies on the line segment connecting them, equidistant from each! Choice A correctly applies the distance formula as the modulus of the difference and the midpoint formula as the average of the two complex numbers. Choice C calculates distance by just subtracting complex numbers without taking the modulus: the difference -4 + 8i (or 4 - 8i) is a vector, not a distance—you must find its length (modulus) to get the distance, so always take the modulus of the difference, don't stop at subtraction! Distance formula for complex numbers: (1) Subtract the complex numbers (order doesn't matter for distance): z₁ - z₂; (2) Find modulus of result: if difference is p + qi, modulus = √(p² + q²); (3) That's the distance—example: distance from 2 - 3i to 5 + i: difference = (2 - 3i) - (5 + i) = -3 - 4i, modulus = √(9 + 16) = 5, and the formula is symmetric—same answer if you subtract in the opposite order. Midpoint formula: (1) Add the two complex numbers: (a + bi) + (c + di) = (a + c) + (b + d)i; (2) Divide result by 2: real part (a + c)/2, imaginary part (b + d)/2; (3) Write as ((a + c)/2) + ((b + d)/2)i—essentially, average x-coordinates for real part, average y-coordinates for imaginary part, just like coordinate midpoint—for 4 + 2i and 2 - 6i: add to get 6 - 4i, divide by 2 to get 3 - 2i as midpoint—the complex plane formulas are identical to coordinate geometry because the complex plane is a coordinate system!
On the complex plane, $z=a+bi$ corresponds to the point $(a,b)$. For $z_1=-1+4i$ and $z_2=3$, which complex number is the midpoint of the segment connecting them, using $\dfrac{z_1+z_2}{2}$?
$-2+2i$
$1+2i$
$2+4i$
$1+4i$
Explanation
This question tests your understanding of finding midpoints between complex numbers on the complex plane using formulas that mirror 2D coordinate geometry. The midpoint formula works the same: midpoint = (z₁ + z₂)/2 = ((a + c)/2) + ((b + d)/2)i, averaging the real parts and imaginary parts separately—these formulas connect complex number arithmetic with geometry beautifully. For the midpoint of -1 + 4i and 3 + 0i: (1) Add: (-1 + 4i) + (3 + 0i) = 2 + 4i; (2) Divide by 2: (2 + 4i)/2 = 1 + 2i, exactly halfway between the two points on the complex plane—geometrically, plot both points and the midpoint lies on the line segment connecting them, equidistant from each! Choice A correctly applies the midpoint formula as the average of the two complex numbers. Choice B makes an arithmetic error by adding instead of averaging: (-1 + 4i) + (3 + 0i) = 2 + 4i, but you must divide the entire result by 2—midpoint formula: add both complex numbers first, then divide by 2, averaging both real and imaginary parts. Midpoint formula: (1) Add the two complex numbers: (a + bi) + (c + di) = (a + c) + (b + d)i; (2) Divide result by 2: real part (a + c)/2, imaginary part (b + d)/2; (3) Write as ((a + c)/2) + ((b + d)/2)i—essentially, average x-coordinates for real part, average y-coordinates for imaginary part, just like coordinate midpoint! For 4 + 2i and 2 - 6i: add to get 6 - 4i, divide by 2 to get 3 - 2i as midpoint—the complex plane formulas are identical to coordinate geometry because the complex plane is a coordinate system, and great job tackling these!
On the complex plane, the midpoint of the segment joining $z_1=4-i$ and $z_2=2+5i$ is $\dfrac{z_1+z_2}{2}=\left(\dfrac{a+c}{2}\right)+\left(\dfrac{b+d}{2}\right)i$, the same as the coordinate midpoint formula. What is the midpoint?
$6+4i$
$3+4i$
$3+2i$
$1+2i$
Explanation
This question tests your understanding of finding midpoints between complex numbers on the complex plane using formulas that mirror 2D coordinate geometry. The midpoint formula works the same: midpoint = (z₁ + z₂)/2 = ((a + c)/2) + ((b + d)/2)i, averaging the real parts and imaginary parts separately—these formulas connect complex number arithmetic with geometry beautifully. For the midpoint of 4 - i and 2 + 5i: (1) Add: (4 - i) + (2 + 5i) = 6 + 4i; (2) Divide by 2: (6 + 4i)/2 = 3 + 2i, exactly halfway between the two points on the complex plane—geometrically, plot both points and the midpoint lies on the line segment connecting them, equidistant from each! Choice A correctly applies the midpoint formula as the average of the two complex numbers. Choice B makes an arithmetic error by adding instead of averaging: (4 - i) + (2 + 5i) = 6 + 4i, but you must divide the entire result by 2—midpoint formula: add both complex numbers first, then divide by 2, averaging both real and imaginary parts. Midpoint formula: (1) Add the two complex numbers: (a + bi) + (c + di) = (a + c) + (b + d)i; (2) Divide result by 2: real part (a + c)/2, imaginary part (b + d)/2; (3) Write as ((a + c)/2) + ((b + d)/2)i—essentially, average x-coordinates for real part, average y-coordinates for imaginary part, just like coordinate midpoint! For 4 + 2i and 2 - 6i: add to get 6 - 4i, divide by 2 to get 3 - 2i as midpoint—the complex plane formulas are identical to coordinate geometry because the complex plane is a coordinate system, and you're doing great mastering this!
Two points on the complex plane are $z_1=-4+1i$ and $z_2=2-5i$. Using the coordinate-geometry distance formula written for complex numbers, $|z_1-z_2|=\sqrt{(a-c)^2+(b-d)^2}$, what is the distance between them?
$6-6i$
$\sqrt{72}$
$\sqrt{36-36}$
$\sqrt{18}$
Explanation
This question tests your understanding of finding distances between complex numbers on the complex plane using formulas that mirror 2D coordinate geometry. The distance between two complex numbers z₁ = a + bi and z₂ = c + di is the modulus of their difference: distance = |z₁ - z₂| = √((a - c)² + (b - d)²), which is exactly the 2D distance formula because the complex plane is a coordinate system—these formulas connect complex number arithmetic with geometry beautifully. To find the distance from -4 + i to 2 - 5i: (1) Calculate difference: (-4 + i) - (2 - 5i) = -6 + 6i; (2) Find modulus: |-6 + 6i| = √(36 + 36) = √72; (3) Distance is √72 units—geometrically, plot both points and the distance is the straight-line length connecting them! Choice B correctly applies the distance formula as the modulus of the difference. Choice A calculates by just subtracting complex numbers without taking the modulus: the difference -6 + 6i is a vector, not a distance—you must find its length (modulus) to get the distance, so always take the modulus of the difference, don't stop at subtraction! Distance formula for complex numbers: (1) Subtract the complex numbers (order doesn't matter for distance): z₁ - z₂; (2) Find modulus of result: if difference is p + qi, modulus = √(p² + q²); (3) That's the distance—example: distance from 2 - 3i to 5 + i: difference = (2 - 3i) - (5 + i) = -3 - 4i, modulus = √(9 + 16) = 5, and the formula is symmetric—same answer if you subtract in the opposite order. Simplifying √72 to 6√2 is optional, but the form matches—you're doing wonderfully!
The distance between $z_1=a+bi$ and $z_2=c+di$ is the modulus $|z_1-z_2|=\sqrt{(a-c)^2+(b-d)^2}$. What is the distance between $z_1=0$ and $z_2=6+8i$?
$\sqrt{28}$
$10$
$14$
$6+8i$
Explanation
This question tests your understanding of finding distances between complex numbers on the complex plane using formulas that mirror 2D coordinate geometry. The distance between two complex numbers z₁ = a + bi and z₂ = c + di is the modulus of their difference: distance = |z₁ - z₂| = √((a - c)² + (b - d)²), which is exactly the 2D distance formula because the complex plane is a coordinate system! The midpoint formula also works the same: midpoint = (z₁ + z₂)/2 = ((a + c)/2) + ((b + d)/2)i, averaging the real and imaginary parts separately—these formulas connect complex number arithmetic with geometry beautifully. To find the distance from 0 to 6 + 8i: (1) Difference: -6 - 8i; (2) Modulus: √(36 + 64) = √100 = 10; (3) Distance is 10 units—from origin! Choice B correctly applies it. Choice D is the number itself—take modulus of difference! Strategy: Subtract, modulus! Example: from 0 to 5 - 12i: √(25+144)=13—fantastic effort!