Algebra II : Understanding Quadratic Equations

Study concepts, example questions & explanations for Algebra II

varsity tutors app store varsity tutors android store

Example Questions

Example Question #4 : How To Multiply Binomials With The Distributive Property

Expand:

\displaystyle (x-9)(3x+2)

Possible Answers:

\displaystyle 3x^{2}-25x-18

\displaystyle 3x^{2}-29x-18

\displaystyle 3x^{2}-18x-29

None of the other answers

\displaystyle 3x^{2}-18x-25

Correct answer:

\displaystyle 3x^{2}-25x-18

Explanation:

To multiple these binomials, you can use the FOIL method to multiply each of the expressions individually.This will give you

\displaystyle (x)(3x)+(x)(2)+(-9)(3x)+(-9)(2)

or \displaystyle 3x^{2}-25x-18.

Example Question #31 : Trinomials

Evaluate the following:

\displaystyle \left(\frac{1}{2}x^2 +2x - 4\right) + \left(\frac{3}{2}x^2 -5x -4\right)

Possible Answers:

\displaystyle x^2+3x-8

\displaystyle 2x^2+3x+8

\displaystyle 2x^2-3x-8

\displaystyle 2x^2-3x

Correct answer:

\displaystyle 2x^2-3x-8

Explanation:

To add these two trinomials, you will first begin by combining like terms. You have two terms with \displaystyle x^2, two terms with \displaystyle x, and two terms with no variable. For the two fractions with \displaystyle x^2, you can immediately add because they have common denominators:

\displaystyle (\frac{1}{2}x^2 +2x - 4) + (\frac{3}{2}x^2 -5x -4)

\displaystyle \frac{4}{2}x^2 -3x - 8

\displaystyle 2x^2 -3x - 8

 

Example Question #12 : Understanding Quadratic Equations

Simplify.

\displaystyle \small \small \frac{x^2+5x+6}{x^3+2x^2-16x-32}

Possible Answers:

\displaystyle \small \small \frac{x-3}{(x-4)(x+4)}

\displaystyle \small \small \frac{x+3}{(x-2)(x+4)}

\displaystyle \small \small \frac{x-2}{(x-4)(x+4)}

\displaystyle \small \frac{x+3}{(x-4)(x+4)}

\displaystyle \small \small \frac{x+3}{(x+4)(x+4)}

Correct answer:

\displaystyle \small \frac{x+3}{(x-4)(x+4)}

Explanation:

Factoring the expression gives \displaystyle \small \frac{}{}\displaystyle \small \small \frac{(x+3)(x+2)}{(x-4)(x+4)(x+2)}. Values that are in both the numerator and denominator can be cancelled. By cancelling \displaystyle \small x+2, the expression becomes \displaystyle \small \small \frac{(x+3)}{(x-4)(x+4)}.

Example Question #13 : Understanding Quadratic Equations

Simplfy.

\displaystyle \small \frac{x^2-2x-15}{x^2-3x-10}

Possible Answers:

\displaystyle \small \small \frac{x-3}{x+2}

\displaystyle \small \frac{x+3}{x+2}

\displaystyle \small \small \small \frac{x-2}{x+3}

\displaystyle \small \small \frac{x+2}{x+3}

\displaystyle \small \small \frac{x+3}{x-2}

Correct answer:

\displaystyle \small \frac{x+3}{x+2}

Explanation:

By factoring the equation you get \displaystyle \small \small \small \frac{(x+3)(x-5)}{(x+2)(x-5)}. Values that are in both the numerator and denominator can be cancelled. Cancelling the \displaystyle \small x-5 values gives \displaystyle \small \small \small \frac{x+3}{x+2}.

Example Question #14 : Understanding Quadratic Equations

Expand.

\displaystyle \small 2(x+2)(x+4)

Possible Answers:

\displaystyle \small x^2+4x+8

\displaystyle \small \small 2x^2+12x-16

\displaystyle \small 2x^2+12x+16

\displaystyle \small \small x^2+4x-8

\displaystyle \small 2x+12x+16

Correct answer:

\displaystyle \small 2x^2+12x+16

Explanation:

By foiling the binomials, multiplying the firsts, then the outers, followed by the inners and lastly the lasts, the expression you get is:

 \displaystyle \small 2(x^2+4x+2x+8).

However, the expression can not be considered simplified in this state.

Distributing the two and adding like terms gives \displaystyle \small 2x^2+12x+16.

Example Question #15 : Understanding Quadratic Equations

If \displaystyle (ax+b)(2ax+3b)=8x^2+30x+27, what is the value of \displaystyle a-b?

Possible Answers:

\displaystyle -24

\displaystyle -15

\displaystyle 15

\displaystyle -1

\displaystyle 18

Correct answer:

\displaystyle -1

Explanation:

Use the FOIL method to simplify the binomial.

\displaystyle (a+b)(c+d) = ac+ad+bc+bd

\displaystyle (ax)(2ax)+(ax)(3b)+(b)(2ax)+(b)(3b)

Simplify the terms.

\displaystyle 2a^2x^2+5abx+3b^2=8x^2+30x+27

Notice that the coefficients can be aligned to the unknown variables.  Solve for \displaystyle a and \displaystyle b.

\displaystyle 2a^2 = 8 \rightarrow a^2 = 4 \rightarrow a=2

\displaystyle 3b^2 = 27\rightarrow b^2=9 \rightarrow b=3

\displaystyle a-b = 2-3 = -1

The answer is:  \displaystyle -1

Example Question #16 : Understanding Quadratic Equations

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

Possible Answers:

\displaystyle 3x^4-4x^3+4x^2-4x-3

\displaystyle 3x^4-4x^3+x^2-2x-3

\displaystyle 3x^4-3x^3-x^2+2x-3

\displaystyle \textup{The answer is not given.}

\displaystyle 3x^4-3x^3-x^2-2x-3

Correct answer:

\displaystyle 3x^4-4x^3+x^2-2x-3

Explanation:

Multiply each term of the first trinomial by second trinomial.

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

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

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

Add and combine like-terms.

The answer is:  \displaystyle 3x^4-4x^3+x^2-2x-3

Example Question #17 : Understanding Quadratic Equations

Simplify the function, if possible:  \displaystyle \frac{8x-10+2x^2}{-16+16x}

Possible Answers:

\displaystyle \frac{3}{16}x-\frac{3}{16}

\displaystyle \frac{1}{8}x+\frac{5}{8}

\displaystyle \frac{1}{16}x-\frac{5}{16}

\displaystyle \textup{The expression cannot be factored.}

\displaystyle \frac{1}{16}x+\frac{5}{16}

Correct answer:

\displaystyle \frac{1}{8}x+\frac{5}{8}

Explanation:

The expression will need to be rearranged from highest to lowest powers in order to be simplified.

\displaystyle \frac{8x-10+2x^2}{-16+16x} =\frac{2x^2+8x-10}{16x-16}

Factor a 2 in the numerator.

\displaystyle 2x^2+8x-10 = 2(x^2+4x-5)

Factor the term in parentheses.

\displaystyle 2(x^2+4x-5) = 2(x-1)(x+5)

Factor the denominator.

\displaystyle 16x-16 = 16(x-1)

Divide the numerator with the denominator.

\displaystyle \frac{2(x-1)(x+5)}{16(x-1)}

The expression becomes:

 \displaystyle \frac{x+5}{8}

The answer is:  \displaystyle \frac{1}{8}x+\frac{5}{8}

Example Question #18 : Understanding Quadratic Equations

Solve for x:

 

\displaystyle \frac{6}{x}=\frac{x+2}{4}

Possible Answers:


None of the other answers

\displaystyle -6,4

\displaystyle 12,-2

\displaystyle -12,2

\displaystyle -4,6

Correct answer:

\displaystyle -6,4

Explanation:

The correct answer is \displaystyle x=-6 or \displaystyle x=4. The first step of the problem is to cross multiply. This will give the following equation:

\displaystyle 24=x^2+2x

 

After subtracting \displaystyle 24 from each side the equation looks like:

 

\displaystyle 0=x^2+2x-24

 

The expression on the right hand side can be factored into: 

\displaystyle 0=(x-4)(x+6 )

 

Both \displaystyle 4 and \displaystyle 6 satisfy the above equation and are therefore the correct answers. 

Example Question #1542 : High School Math

Expand this expression:

\displaystyle (x-4)\displaystyle (2x+4)

Possible Answers:

\displaystyle 2x^2 - 4x + 16

\displaystyle 2x^2 - 4x - 16

\displaystyle 2x^2 + 4x - 16

\displaystyle 2x - 4x - 16

\displaystyle 2x^2 + 4x + 16

Correct answer:

\displaystyle 2x^2 - 4x - 16

Explanation:

Use the FOIL method (First, Outer, Inner, Last):

\displaystyle x * 2x = 2x^2

\displaystyle x * 4 = 4x

\displaystyle -4 * 2x = -8x

\displaystyle -4 * 4 = -16

Put all of these terms together:

\displaystyle 2x^2 + 4x - 8x - 16

Combine like terms:

\displaystyle 2x^2 - 4x - 16

Learning Tools by Varsity Tutors