Algebra - ACT Math

Card 0 of 11421

Question

Expand the following expression:

(B – 2) (B + 4)

Answer

Here we use FOIL:

Firsts: B * B = B2

Outer: B * 4 = 4B

Inner: –2 * B = –2B

Lasts: –2 * 4 = –8

All together this yields

B2 + 2B 8

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Question

What is the product of the two real solutions of x2 + 5x = 6?

Answer

x2 + 5x 6 = 0 factors to (x+6)(x**–**1) = 0.

Therefore, the two real solutions are x = **–**6 and x = 1. Their product is simply **–**6.

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Question

Which of the following is equivalent to (2g – 3h)2?

Answer

Use FOIL: (2g – 3h)(2g – 3h) = 4g2 – 6gh – 6gh + 9h2 = 4g2 – 12gh + 9h2

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Question

If 2x + y = 9 and y – z = 4 then 2x + z = ?

Answer

If we solve the first equation for 2x we find that 2x = 9 – y. If we solve the second equation for z we find z = –4 + y. Adding these two manipulated equations together we see (2x) + (y) = (9 – y)+(–4 + y).

The y’s cancel leaving us with an answer of 5.

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Question

11/(x – 7) + 4/(7 – x) = ?

Answer

We must find a common denominator and here they changed the first fraction by removing a negative from the numerator and denominator, leaving –11/(7 – x). We add the numerators and keep the same denominator to find the answer.

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Question

Which of the following is a factor of the polynomial x_2 – 6_x + 5?

Answer

Factor the polynomial by choosing values that when FOIL'ed will add to equal the middle coefficient, 3, and multiply to equal the constant, 1.

x_2 – 6_x + 5 = (x – 1)(x – 5)

Because only (x – 5) is one of the choices listed, we choose it.

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Question

What is the value of the function f(x) = 6x2 + 16x – 6 when x = –3?

Answer

There are two ways to do this problem. The first way just involves plugging in –3 for x and solving 6〖(–3)〗2 + 16(–3) – 6, which equals 54 – 48 – 6 = 0. The second way involves factoring the polynomial to (6x – 2)(x + 3) and then plugging in –3 for x. The second way quickly shows that the answer is 0 due to multiplying by (–3 + 3).

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Question

Solve for x: (x2 – x) / (x – 1) = 1

Answer

Begin by multiplying both sides by (x – 1):

x2 – x = x – 1

Solve as a quadratic equation: x2 – 2x + 1 = 0

Factor the left: (x – 1)(x – 1) = 0

Therefore, x = 1.

However, notice that in the original equation, a value of 1 for x would place a 0 in the denominator. Therefore, there is no solution.

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Question

Solve 3x2 + 10x = –3

Answer

Generally, quadratic equations have two answers.

First, the equations must be put in standard form: 3x2 + 10x + 3 = 0

Second, try to factor the quadratic; however, if that is not possible use the quadratic formula.

Third, check the answer by plugging the answers back into the original equation.

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Question

What is the value of m where:

Answer

If n=4, then 64(4/12)=64(1/3)=4. Then, 4=mŸ4(1+m)/(m+4). If 2 is substituted for m, then 4=2Ÿ4(1+2)/(2+4)=2Ÿ41/2=2Ÿ√4=2Ÿ2=4.

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Question

Solve the following system of equations:

–2x + 3y = 10

2x + 5y = 6

Answer

Since we have –2x and +2x in the equations, it makes sense to add the equations together to give 8y = 16 yielding y = 2. Then we substitute y = 2 into one of the original equations to get x = –2. So the solution to the system of equations is (–2, 2)

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Question

What is the of the following equation: ?

Answer

The y-intercept is the constant at the end of the equation. Thus for our equation the y-intercept is 7

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Question

What is the equation for a circle of radius 12, centered at the intersection of the two lines:

y_1 = 4_x + 3

and

y_2 = 5_x + 44?

Answer

To begin, let us determine the point of intersection of these two lines by setting the equations equal to each other:

4_x_ + 3 = 5_x_ + 44; 3 = x + 44; –41 = x

To find the y-coordinate, substitute into one of the equations. Let's use _y_1:

y = 4 * –41 + 3 = –164 + 3 = –161

The center of our circle is therefore: (–41, –161).

Now, recall that the general form for a circle with center at (_x_0, _y_0) is:

(x - _x_0)2 + (y - _y_0)2 = _r_2

For our data, this means that our equation is:

(x + 41)2 + (y + 161)2 = 122 or (x + 41)2 + (y + 161)2 = 144

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Question

What is the equation for a circle of radius 9, centered at the intersection of the following two lines?

Answer

To begin, let us determine the point of intersection of these two lines by setting the equations equal to each other:

To find the y-coordinate, substitute into one of the equations. Let's use :

The center of our circle is therefore .

Now, recall that the general form for a circle with center at is

For our data, this means that our equation is:

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Question

The diameter of a circle has endpoints at points (2, 10) and (–8, –14). Which of the following points does NOT lie on the circle?

Answer

Circle_point1

Circle_point2

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Question

The Y axis is a _______________ of the function Y = 1/X

Answer

A line is an asymptote in a graph if the graph of the function nears the line as X or Y gets larger in absolute value.

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Question

What is the domain of the following function:

Answer

The denominator cannot be zero, otherwise the function is indefinite. Therefore x cannot be –2 or –3.

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Question

Circle A is centered about the origin and has a radius of 5. What is the equation of the line that is tangent to Circle A at the point (–3,4)?

Answer

The line must be perpendicular to the radius at the point (–3,4). The slope of the radius is given by Actmath_7_113_q7

The radius has endpoints (–3,4) and the center of the circle (0,0), so its slope is –4/3.

The slope of the tangent line must be perpendicular to the slope of the radius, so the slope of the line is ¾.

The equation of the line is y – 4 = (3/4)(x – (–3))

Rearranging gives us: 3_x_ – 4_y_ = -25

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Question

Give the equation, in slope-intercept form, of the line tangent to the circle of the equation

at the point .

Answer

Rewrite the equation of the circle in standard form to find its center:

Complete the square:

The center is .

A tangent to this circle at a given point is perpendicular to the radius to that point. The radius with endpoints and will have slope

,

so the tangent line has the opposite of the reciprocal of this, or , as its slope.

The tangent line therefore has equation

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Question

Give the equation, in slope-intercept form, of the line tangent to the circle of the equation

at the point .

Answer

The graph of the equation is a circle with center .

A tangent to this circle at a given point is perpendicular to the radius to that point. The radius with endpoints and will have slope

,

so the tangent line has the opposite of the reciprocal of this, or , as its slope.

The tangent line therefore has equation

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