SAT Math : SAT Mathematics

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #51 : Algebraic Functions

The function  is defined as . What is  ?

Possible Answers:

-36

56

36

18

24

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 #2911 : Sat Mathematics

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 #2912 : Sat Mathematics

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

Possible Answers:

x = -4, x = -2

x = -4, x = 2

x = -5, x = 1

x = -3, x = 4

x = 8, x = 0

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+4

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

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

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

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 .

Example Question #2 : How To Use The Quadratic Function

If , which two values of  are correct?

Possible Answers:

Correct answer:

Explanation:

First, set the quadratic function equal to :

Then, separate the function into its two component factors:

It follows from this equation that either  or 

Example Question #2 : How To Use The Quadratic Function

The length of a rectangular piece of land is two feet more than three times its width. If the area of the land is , what is the width of that piece of land?

Possible Answers:

Correct answer:

Explanation:

The area of a rectangle is the product of its length by its width, which we know to be equal to  in our problem. We also know that the length is equal to , where  represents the width of the land. Therefore, we can write the following equation:

Distributing the  outside the parentheses, we get:

Subtracting  from each side of the equation, we get:

We get a quadratic equation, and since there is no factor of  and  that adds up to , we use the quadratic formula to solve this equation.

           

We can first calculate the discriminant (i.e. the part under the square root)

 

We replace that value in the quadratic formula, solving both the positive version of the formula (on the left) and the negative version of the formula (on the right):

                                                              

Breaking down the square root:

                          

We can pull two of the twos out of the square root and place a  outside of it:

                  

We can then multiply the  and the :

                                   

At this point, we can reduce the equations, since each of the component parts of their right sides has a factor of :

                                   

Since width is a positive value, the answer is:

 The width of the piece of land is approximately .

Example Question #2913 : Sat Mathematics

What is the focus of the above quadratic equation?

Possible Answers:

Correct answer:

Explanation:

The focus is solved by using the following formula , where  are the coordinates of the vertex, and  is the distance from the vertex. To solve for , we use

, where  is the coefficient in front of the  term and  is the focus.

 

Since , we can substitute in to get,

Now we need to find the vertex of the equation.

Since our equation is in vertex form, we can deduce that the vertex is at 

So the focus is at 

Example Question #2914 : Sat Mathematics

Find all the solutions of where  crosses the line .

Possible Answers:

 

 

 

No Real Solutions

 

 

Correct answer:

 

Explanation:

In order to find all the solutions, we need to set the equations equal to each other.

Now subtract  and  from each side.

Factor the left hand side to get

Factor the quadratic function inside the parenthesis to get

The solutions to this equation are

 

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