Precalculus : Pre-Calculus

Study concepts, example questions & explanations for Precalculus

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Example Questions

Example Question #1 : Determine The Symmetry Of An Equation

Is the following function symmetrical about the y axis (is it an even function)?

Possible Answers:

Insufficient Information

Not a function

Yes

No

Correct answer:

No

Explanation:

For a function to be even, it must satisfy the equality 

Likewise if a function is even, it is symmetrical about the y-axis 

Therefore, the function is not even, and so the answer is No

Example Question #1 : Determine The Symmetry Of An Equation

Algebraically check for symmetry with respect to the x-axis, y axis, and the origin.

Possible Answers:

Symmetrical about the x-axis

Symmetrical about the origin

Symmetrical about the y-axis

No symmetry

Correct answer:

Symmetrical about the x-axis

Explanation:

For a function to be symmetrical about the y-axis, it must satisfy   so there is not symmetry about the y-axis

For a function to be symmetrical about the x-axis, it must satisfy   so there is symmetry about the x-axis

For a function to be symmetrical about the origin, you must replace y with (-y) and x with (-x) and the resulting function must be equal to the original function.

 

-So there is no symmetry about the origin, and the answer is Symmetrical about the x-axis

Example Question #1 : Determine The Symmetry Of An Equation

Algebraically check for symmetry with respect to the x-axis, y axis, and the origin.

Possible Answers:

Symmetry about the x-axis, and y-axis

Symmetry about the x-axis

Symmetry about the y-axis 

Symmetry about the y-axis and origin

Symmetry about the x-axis, y-axis, and origin

Correct answer:

Symmetry about the y-axis 

Explanation:

For a function to be symmetrical about the y-axis, it must satisfy  so there is symmetry about the y-axis

For a function to be symmetrical about the x-axis, it must satisfy  

 so there is not symmetry about the x-axis

For a function to be symmetrical about the origin, you must replace y with (-y) and x with (-x) and the resulting function must be equal to the original function.

 

So there is no symmetry about the origin.

Example Question #1 : Determine The Symmetry Of An Equation

Algebraically check for symmetry with respect to the x-axis, y-axis, and the origin. 

Possible Answers:

Symmetry about the x-axis and y-axis

Symmetry about the x-axis, y-axis, and origin

Symmetry about the y-axis

Symmetry about the x-axis

Symmetry about the y-axis and the origin

Correct answer:

Symmetry about the y-axis

Explanation:

For a function to be symmetrical about the y-axis, it must satisfy 

 so there is symmetry about the y-axis

For a function to be symmetrical about the x-axis, it must satisfy 

 so there is not symmetry about the x-axis

For a function to be symmetrical about the origin, you must replace y with (-y) and x with (-x) and the resulting function must be equal to the original function.

So there is no symmetry about the origin, and the credited answer is "symmetry about the y-axis".

Example Question #1 : Determine The Symmetry Of An Equation

Which of the following best describes the symmetry of   with respect to the x-axis, y-axis, and the origin.

Possible Answers:

No symmetry

Symmetrical about the y-axis

Symmetrical about the x-axis

Symmetrical about the origin

Correct answer:

Symmetrical about the x-axis

Explanation:

For a function to be symmetrical about the y-axis, it must satisfy 

 so there is not symmetry about the y-axis

For a function to be symmetrical about the x-axis, it must satisfy 

 so there is symmetry about the x-axis

For a function to be symmetrical about the origin, you must replace y with (-y) and x with (-x), and the resulting function must be equal to the original function.

So there is no symmetry about the origin, and the answer is Symmetrical about the x-axis.

Example Question #1 : Determine The Symmetry Of An Equation

Is the following function symmetrical about the y-axis (is it an even function)?

Possible Answers:

Yes

No

The given information does not include a function

There is insufficient information to determine the answer

Correct answer:

No

Explanation:

For a function to be even, it must satisfy the equality

Likewise, if a function is even, it is symmetrical about the y-axis

Therefore, the function is not even, and so the answer is No.

Example Question #1 : Write A Quadratic Equation When Given Its Solutions

Which of the following could be the equation for a function whose roots are at  and ?

Possible Answers:

Correct answer:

Explanation:

If the roots of the equation are at x= -4 and x=3, then we can work backwards to see what equation those roots were derived from. If we factored a quadratic equation and obtained the given solutions, it would mean the factored form looked something like:

Because this is the form that would yield the solutions x= -4 and x=3. If we work backwards and multiply the factors back together, we get the following quadratic equation:

Example Question #1 : Write A Quadratic Equation When Given Its Solutions

Given roots . Write a quadratic polynomial that has as roots.

Possible Answers:

Correct answer:

Explanation:

We can make a quadratic polynomial with  by mutiplying the linear polynomials they are roots of, and multiplying them out.

Start

  

Distribute the negative sign

 

FOIL the two polynomials. This means multiply the firsts, then the outers, followed by the inners and lastly, the last terms.

    

    

Simplify

    

 

Example Question #1 : Write A Quadratic Equation When Given Its Solutions

If we know the solutions of a quadratic equation, we can then build that quadratic equation.

Find the quadratic equation when we know that:

 and  are solutions.

Possible Answers:

Correct answer:

Explanation:

Since we know the solutions of the equation, we know that:

We simply carry out the multiplication on the left side of the equation to get the quadratic equation.

 

Example Question #1 : Write A Quadratic Equation When Given Its Solutions

Which of the following is a quadratic function passing through the points  and ?

Possible Answers:

Correct answer:

Explanation:

These two points tell us that the quadratic function has zeros at , and at .

These correspond to the linear expressions , and .

Expand their product and you arrive at the correct answer.

If the quadratic is opening up the coefficient infront of the squared term will be positive. Thus we get:

.

If the quadratic is opening down it would pass through the same two points but have the equation:

.

Since only  is seen in the answer choices, it is the correct answer.

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