SAT Math › How to simplify an expression
If 6 less than the product of 9 and a number is equal to 48, what is the number?
6
5
4
3
Write an equation for the written expression: 9x – 6 = 48. When we solve for x we get x = 6.
If x y = (5x - 4y)/y , find the value of y if 6
y = 2.
2
4
5
10
If we substitute 6 in for x in the given equation and set our answer to 2, we can solve for y algebraically. 30 minus 4y divided by y equals 2 **-->**2y =30 -4y --> 6y =30 --> y=5. We could also work from the answers and substitute each answer in and solve.
Simplify the expression:
In order to simplify an expression, we rearrange it to put terms with the same base or type of variable together, then add or subtract accordingly. However, because this problem has a minus sign, it first needs to be distributed. That would look as follows:
Given , simplify the following expression.
Taking a look at the given expression, we can see that we have two fractions divided by one another. The first fraction in the numerator is , and the second fraction in the denominator is
.
Remember that when we have a fraction divided by a fraction, that is the same thing as multiplying the numerator by the reciprocal of the denominator. To simplify, we will do just that.
.
To double check your answer, you can choose a numerical value for a and b and plug them into the expression.
Evaluate: (2x + 4)(x2 – 2x + 4)
2x3 – 4x2 + 8x
2x3 – 8x2 + 16x + 16
2x3 + 16
2x3 + 8x2 – 16x – 16
4x2 + 16x + 16
Multiply each term of the first factor by each term of the second factor and then combine like terms.
(2x + 4)(x2 – 2x + 4) = 2x3 – 4x2 + 8x + 4x2 – 8x + 16 = 2x3 + 16
Which of the following does not simplify to ?
All of these simplify to
5x – (6x – 2x) = 5x – (4x) = x
(x – 1)(x + 2) - x2 + 2 = x2 + x – 2 – x2 + 2 = x
x(4x)/(4x) = x
(3 – 3)x = 0x = 0
Simplify the following expression: x3 - 4(x2 + 3) + 15
To simplify this expression, you must combine like terms. You should first use the distributive property and multiply -4 by x2 and -4 by 3.
x3 - 4x2 -12 + 15
You can then add -12 and 15, which equals 3.
You now have x3 - 4x2 + 3 and are finished. Just a reminder that x3 and 4x2 are not like terms as the x’s have different exponents.
Let f(x) be a function, and let a and b represent any numbers belonging to the domain of f(x). If f(a + b) = f(a) + f(b) for all of the possible values of a and b, then f(x) is considered "special." Which of the following functions is special?
f(x) = 2_x_
f(x) = |x|
f(x) = _x_2
f(x) = (x + 1)2 – _x_2
f(x) = (x + 1)2 – (x – 1)2
In order to solve this problem, we need to look at each function separately and then derive expressions for f(a + b), f(a), and f(b). Then, we need to see whether f(a + b) = f(a) + f(b).
Let's start with the function 2_x_.
f(a + b) = 2(a+b)
Using our property of exponents that xyxz = x y+z, we can rewrite 2_a_+b.
f(a + b) = 2(a+b) = 2_a_2_b_
Now, let's derive an expression for f(a) + f(b).
f(a) = 2_a_, and f(b) = 2_b_. Thus, f(a) + f(b) = 2_a_ + 2_b_
Let's compare f(a + b) and f(a) + f(b).
Does 2_a_2_b_ = 2_a_ + 2_b_? It might, but not for every value of a and b. For example, let a and b both equal 0.
2020 = 1(1) = 1
20 + 20 = 1 + 1 = 2
If a and b are both zero, then it isn't true that f(a + b) = f(a) + f(b). Thus, f(x) = 2_x_ isn't special.
Next, let's examine the function f(x) = |x|.
f(a + b) = |a + b|
f(a) + f(b) = |a| + |b|
|a + b| doesn't always equal |a| + |b|. For example, if a = –1 and b = 1, then |a + b| = |–1 + 1| = 0, while f(a) + f(b) = |–1| + |1| = 1 + 1 = 2. Because f(a + b) is not always going to equal f(a) + f(b), the function f(x) = |x| isn't special.
The next function we can analyze is f(x) = _x_2.
f(a + b) = (a + b)2 = a_2 +2_ab + _b_2
f(a) + f(b) = _a_2 + _b_2
a_2 + 2_ab + _b_2 doesn't always equal _a_2 + _b_2 . Thus, f(x) = _x_2 isn't special.
The next function is f(x) = (x + 1)2 – _x_2. We can simplify f(x) a little bit to make it easier to work with.
f(x) = (x + 1)2 – _x_2 = (x_2 + 2_x + 1) – x_2 = 2_x + 1.
f(x) = 2_x_ + 1.
f(a + b) = 2(a + b) + 1 = 2_a_ + 2_b_ + 1
f(a) + f(b) = (2_a_ + 1) + (2_b_ + 1) = 2_a_ + 2_b_ + 2
2_a_ + 2_b_ + 1 doesn't equal 2_a_ + 2_b_ + 2, so this isn't a special function either.
This means that f(x) = (x + 1)2 – (x – 1)2 must be special. Let's see why.
First, let's simplify f(x).
f(x) = (x + 1)2 – (x – 1)2 = (x_2 + 2_x + 1) – (x_2 – 2_x + 1) = x_2 + 2_x + 1 – x_2 + 2_x – 1 = 4_x_.
f(x) = 4_x_.
f(a + b) = 4(a + b) = 4_a_ + 4_b_
f(a) + f(b) = 4_a_ + 4_b_
4_a_ + 4_b_ is always equal to 4_a_ + 4_b_. This means that the function is special.
The answer is f(x) = (x + 1)2 – (x – 1)2 .
Solve for x: 2y/3b = 5x/7a
15b/14ay
7ab/6y
14ay/15b
6ab/7y
5by/3a
Cross multiply to get 14ay = 15bx, then divide by 15b to get x by itself.
If ab = –8, and _a_2 + _b_2 = 20, then what is (a – b)2?
64
16
36
40
4
First, let's expand (a – b)2 using the FOIL method.
(a – b)(a – b) = _a_2 – ab – ba + _b_2 = a_2 – 2_ab + _b_2
The value of _a_2 + b_2 is already given to us. We can manipulate the equation ab = –8 to determine the value of –2_ab. Multiply both sides of the equation by –2.
–2_ab_ = 16
We will now substitute the values of –2_ab_ and _a_2 + _b_2 to find the value of (a – b)2.
(a – b)(a – b) = a_2 – 2_ab + _b_2 = 16 + 20 = 36
The answer is 36.