Precalculus : Pre-Calculus

Study concepts, example questions & explanations for Precalculus

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Example Questions

Example Question #23 : Polynomial Functions

Zeros of a quadratic.

Find the zeros of

\(\displaystyle f(x)=x^2-5x-36\).

Possible Answers:

\(\displaystyle x=\{-9,0\}\).

\(\displaystyle x=\{0,-9\}\).

\(\displaystyle x=\{-4,9\}\).

\(\displaystyle x=\{45.2,0.2\}\)

\(\displaystyle x=\{\frac{45}{2},-0\}\).

Correct answer:

\(\displaystyle x=\{-4,9\}\).

Explanation:

\(\displaystyle (-9)(4)=-36\), and \(\displaystyle -9+4=-5\), so the polynomial factors into

\(\displaystyle (x-9)(x+4)\).

When the function is set to equal 0, either of the products that it factors into are 0. That is

\(\displaystyle x-9=0\),

so \(\displaystyle x=9.\)

And

\(\displaystyle x+4=0\),

so \(\displaystyle x=-4\).

 

Example Question #101 : Pre Calculus

Find the zeros of the following polynomial:

\(\displaystyle x^2-12x+36\)

Possible Answers:

\(\displaystyle 6,3\)

\(\displaystyle 6\)

\(\displaystyle -6\)

\(\displaystyle 3\)

\(\displaystyle 5\)

Correct answer:

\(\displaystyle 6\)

Explanation:

To find the zeros, we must set it equal to zero, factor, and solve.

\(\displaystyle x^2-12x+36=0\)

\(\displaystyle (x-6)^2=0\)

\(\displaystyle x=6\)

Example Question #102 : Pre Calculus

Simplify the following expression:

\(\displaystyle x^4y^3z^2*x^2y^3z^4\)

Possible Answers:

\(\displaystyle \frac{z^2}{x^2}\)

\(\displaystyle \frac{x^2}{z^2}\)

\(\displaystyle x^2z^2\)

\(\displaystyle \frac{1}{x^6y^6z^6}\)

\(\displaystyle x^6y^6z^6\)

Correct answer:

\(\displaystyle x^6y^6z^6\)

Explanation:

When multiplying polynomials, add their exponents.

\(\displaystyle x:4+2=6\)

\(\displaystyle y:3+3=6\)

\(\displaystyle z:2+4=6\)

\(\displaystyle x^6y^6z^6\)

Example Question #103 : Pre Calculus

Simplify this polynomial:

\(\displaystyle \frac{x^4y^3z^2}{x^2y^3z^4}\)

Possible Answers:

\(\displaystyle \frac{x^2}{z^2}\)

\(\displaystyle \frac{1}{x^6y^6z^6}\)

\(\displaystyle \frac{z^2}{x^2}\)

\(\displaystyle x^6y^6z^6\)

Correct answer:

\(\displaystyle \frac{x^2}{z^2}\)

Explanation:

When dividing polynomials, you must subtract corresponding exponents.

\(\displaystyle x:4-2=2\)

\(\displaystyle y:3-3=0\)

\(\displaystyle z:2-4=-2\)

Thus, our answer is

\(\displaystyle x^2y^0z^{-2}=\frac{x^2}{z^2}\).

Example Question #104 : Pre Calculus

Simplify the following:

\(\displaystyle \frac{x^4y^{-1}z^2}{x^{-3}y^2z^2}\)

Possible Answers:

\(\displaystyle \frac{x^7z^4}{y^2}\)

\(\displaystyle \frac{x^7}{y^3}\)

\(\displaystyle \frac{x}{y^3}\)

\(\displaystyle \frac{x}{y}\)

Correct answer:

\(\displaystyle \frac{x^7}{y^3}\)

Explanation:

When dividing, we must subtract the exponents.

\(\displaystyle x:4-(-3)=7\)

\(\displaystyle y=-1-2=-3\)

\(\displaystyle z=2-2=0\)

Thus, our answer is  \(\displaystyle \frac{x^7}{y^3}\).

Example Question #105 : Pre Calculus

A polynomial with leading term \(\displaystyle x^3\) has roots 1,2, and 3. What is the polynomial?

Possible Answers:

\(\displaystyle x^3+6x^2-11x+6\)

\(\displaystyle x^3-3x^2+2x-1\)

\(\displaystyle x^3+3x^2-2x+1\)

\(\displaystyle x^3-6x^2+11x-6\)

Correct answer:

\(\displaystyle x^3-6x^2+11x-6\)

Explanation:

Given the roots of a polynomial, the problem can be solved in reverse. For 3,2, and 1 to be roots, the following must be true:

\(\displaystyle (x-3)(x-2)(x-1)=0\)

Therefore, expand the left side of the equation to find the polynomial.

\(\displaystyle (x^2-5x+6)(x-1)\)

\(\displaystyle x^3-5x^2+6x-x^2+5x-6\)

\(\displaystyle x^3-6x^2+11x-6\)

Example Question #106 : Pre Calculus

Solve for x:

\(\displaystyle x(x-2)=3\)

Possible Answers:

\(\displaystyle 2,-3\)

\(\displaystyle 3,-2\)

\(\displaystyle -3,1\)

\(\displaystyle 3,-1\)

Correct answer:

\(\displaystyle 3,-1\)

Explanation:

To solve, we must expand, factor, and solve.

\(\displaystyle x(x-2)=3\)

\(\displaystyle x^2-2x=3\)

\(\displaystyle x^2-2x-3=0\)

\(\displaystyle (x-3)(x+1)=0\)

\(\displaystyle x=3,-1\)

Example Question #1 : Solving Polynomial Equations

Solve the following for x:

\(\displaystyle x^2(x+3)=4x\)

Possible Answers:

\(\displaystyle -4,1\)

\(\displaystyle -4,0,1\)

\(\displaystyle 4,-1\)

\(\displaystyle 4,0,-1\)

Correct answer:

\(\displaystyle -4,0,1\)

Explanation:

To solve, we must expand, factor, and solve for x.

\(\displaystyle x^2(x+3)=4x\)

\(\displaystyle x^3+3x^2-4x=0\)

\(\displaystyle x(x+4)(x-1)=0\)

\(\displaystyle x=0,-4,1\)

Example Question #4 : Solving Polynomial Equations

Given the polynomial \(\displaystyle \small 4x^{3}+3x^{2}-hx-9\), determine the value of \(\displaystyle \small h\)

 given that the polynomial is exactly divisable by \(\displaystyle \small x+3\)

Possible Answers:

\(\displaystyle \small \small h=2\)

\(\displaystyle \small \small h=-3\)

\(\displaystyle \small \small h=3\)

\(\displaystyle \small h=30\)

\(\displaystyle \small \small h=90\)

Correct answer:

\(\displaystyle \small h=30\)

Explanation:

First determine the value of x by setting \(\displaystyle \small x+3\) equal to 0.

\(\displaystyle \small x+3 =0\)

\(\displaystyle \small x=-3\)

Next, plug in the value of x determined above into the polynomial. The polynomial is to be set equal to 0. Solve for the value of h.

\(\displaystyle \small \small \small 4(-3)^{3}+3(-3))^{2}-(-3)h-9=0\)

\(\displaystyle \small -108+27+3h-9=0\)

\(\displaystyle \small 3h-90=0\)

\(\displaystyle \small 3h=90\)

\(\displaystyle \small h=30\)

Example Question #3 : Solving Polynomial Equations

Solve the following for x:

\(\displaystyle x^2(x-6)=16x\)

Possible Answers:

\(\displaystyle -2,0,8\)

\(\displaystyle -2,8\)

\(\displaystyle -1,0,16\)

\(\displaystyle 0\)

\(\displaystyle -8,0,2\)

Correct answer:

\(\displaystyle -2,0,8\)

Explanation:

To solve, we must expand, factor, and solve for x.

\(\displaystyle x^2(x-6)=16x\)

\(\displaystyle x^3-6x^2-16x=0\)

\(\displaystyle x(x-8)(x+2)=0\)

\(\displaystyle x=-2,0,8\)

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