SAT Math : Algebra

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #13 : How To Find F(X)

If , then  

Possible Answers:

Correct answer:

Explanation:

,

Example Question #161 : How To Find F(X)

Define two functions as follows:

Evaluate .

Possible Answers:

Correct answer:

Explanation:

By definition, .

First, evaluate  by setting  in the definition of :

, so evaluate  similarly:

Example Question #162 : How To Find F(X)

Define , restricting the domain of the function to the interval .

Give the range of the function.

Possible Answers:

None of these

Correct answer:

Explanation:

If , then, by way of the properties of inequality, we can multiply all expressions by 2:

then add 3 to all expressions:

Taking the square root of all expressions, we get

So

.

The correct range is .

Example Question #201 : Algebraic Functions

Define two functions as follows:

Evaluate:

Possible Answers:

None of these

Correct answer:

Explanation:

By definition, .

First, evaluate  by setting  in the definition of :

, so evaluate  similarly:

Example Question #33 : Algebraic Functions

The function  is defined as . What is  ?

Possible Answers:

24

56

18

36

-36

Correct answer:

24

Explanation:

Substitute -1 for  in the given function.

If you didn’t remember the negative sign, you will have calculated 36. If you remembered the negative sign at the very last step, you will have calculated -36; however, if you did not remember that  is 1, then you will have calculated 18.

Example Question #34 : Algebraic Functions

If the function  is created by shifting  up four units and then reflecting it across the x-axis, which of the following represents  in terms of ?

Possible Answers:

Correct answer:

Explanation:

We can take each of the listed transformations of  one at a time. If  is to be shifted up by four units, increase every value of  by 4. 

Next, take this equation and reflect it across the x-axis. If we reflect a function across the x-axis, then all of its values will be multiplied by negative one. So,  can be written in the following way:

Lastly, distribute the negative sign to arrive at the final answer.

Example Question #1 : How To Use The Quadratic Function

If x + 2x - 1 = 7, which answers for x are correct?

Possible Answers:

x = -4, x = 2

x = -3, x = 4

x = -5, x = 1

x = 8, x = 0

x = -4, x = -2

Correct answer:

x = -4, x = 2

Explanation:

x + 2x - 1 = 7

x + 2x - 8 = 0

(x + 4) (x - 2) = 0

x = -4, x = 2

Example Question #2 : How To Use The Quadratic Function

Which of the following quadratic equations has a vertex located at \dpi{100} (3,4)?

Possible Answers:

f(x)=-2x^2+12x-12

f(x)=-2x^2+12x-14

f(x)=-2x^2-12x+4

f(x)=-2x^2-12x+58

f(x)=-2x^2+8x-2

Correct answer:

f(x)=-2x^2+12x-14

Explanation:

The vertex form of a parabola is given by the equation:

f(x)=a(x-h)^2 +k, where the point \dpi{100} (h,k) is the vertex, and \dpi{100} a is a constant.

We are told that the vertex must occur at \dpi{100} (3,4), so let's plug this information into the vertex form of the equation. \dpi{100} h will be 3, and \dpi{100} k will be 4.

f(x)=a(x-3)^2 +4

Let's now expand (x-3)^2 by using the FOIL method, which requires us to multiply the first, inner, outer, and last terms together before adding them all together.

(x-3)^2 = (x-3)(x-3)=x^2-3x-3x+9=x^2-6x+9

We can replace (x-3)^2 with x^2-6x+9.

f(x)=a(x-3)^2+4=a(x^2-6x+9)+4

Next, distribute the \dpi{100} a.

a(x^2-6x+9)+4 = ax^2 -6ax+9a+4

Notice that in all of our answer choices, the first term is -2x^2. If we let \dpi{100} a=-2, then we would have -2x^2 in our equation. Let's see what happens when we substitute \dpi{100} -2 for \dpi{100} a.

f(x)=ax^2-6ax+9a+4=(-2)x^2-6(-2)x+9(-2)+4

=-2x^2+12x-18+4

Example Question #1 : How To Use The Quadratic Function

If , which two values of  are correct?

Possible Answers:

Correct answer:

Explanation:

First, we set the quadratic function equal to :

Reduce the function to its two component factors:

Therefore, since either  or ,

Example Question #2 : How To Use The Quadratic Function

If , which pair of values for  are correct?

Possible Answers:

Correct answer:

Explanation:

First, set the quadratic function equal to :

Then, reduce the function to its two factors:

Since one of the factors on the left hand side of the equation must equal  in order for the above equation to be true,

 or 

Solving for both, we get .

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