ACT Math : Expressions

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #2 : Expressions

Simplify the following rational expression: (9x - 2)/(x2) MINUS (6x - 8)/(x2)

Possible Answers:

\(\displaystyle \frac{12x-6}{x}\)

\(\displaystyle \frac{15x+6}{x}\)

\(\displaystyle \frac{3x+6}{x^{2}}\)

\(\displaystyle 3x-10\)

Correct answer:

\(\displaystyle \frac{3x+6}{x^{2}}\)

Explanation:

Since both expressions have a common denominator, x2, we can just recopy the denominator and focus on the numerators. We get (9x - 2) - (6x - 8). We must distribute the negative sign over the 6x - 8 expression which gives us 9x - 2 - 6x + 8 ( -2 minus a -8 gives a +6 since a negative and negative make a positive). The numerator is therefore 3x + 6.

Example Question #1 : Expressions

Simplify the following rational expression:

\(\displaystyle \frac{7x-18}{x^{2}}+\frac{6x-14}{x^{2}}\)

 

Possible Answers:

\(\displaystyle \frac{x-4}{x^{2}}\)

\(\displaystyle \frac{13x-32}{x^{2}}\)

\(\displaystyle \frac{x-32}{x^{2}}\)

\(\displaystyle \frac{13x-4}{x^{2}}\)

\(\displaystyle \frac{13x-28}{x^{2}}\)

Correct answer:

\(\displaystyle \frac{13x-32}{x^{2}}\)

Explanation:

Since both fractions in the expression have a common denominator of \(\displaystyle x^{2}\), we can combine like terms into a single numerator over the denominator:

\(\displaystyle \frac{7x-18}{x^{2}}+\frac{6x-14}{x^{2}}\)

\(\displaystyle =\frac{(7x-18)+(6x-14)}{x^{2}}\)

\(\displaystyle =\frac{13x-32}{x^{2}}\)

Example Question #702 : Algebra

Simplify the following expression:

\(\displaystyle \frac{10x-9}{x^{3}}+\frac{11x+12}{x^{3}}\)

Possible Answers:

\(\displaystyle \frac{21x+3}{x^{3}}\)

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

\(\displaystyle \frac{21x-3}{x^3}\)

\(\displaystyle \frac{3-21x}{x^{3}}\)

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

Correct answer:

\(\displaystyle \frac{21x+3}{x^{3}}\)

Explanation:

Since both terms in the expression have the common denominator \(\displaystyle x^{3}\), combine the fractions and simplify the numerators:

\(\displaystyle \frac{10x-9}{x^{3}}+\frac{11x+12}{x^{3}}\)

\(\displaystyle =\frac{(10x-9)+(11x+12)}{x^{3}}\)

\(\displaystyle =\frac{21x+3}{x^{3}}\)

Example Question #2 : How To Add Rational Expressions With A Common Denominator

Simplify the following rational expression:

\(\displaystyle \frac{5x-5}{2x^{2}} + \frac{7x+9}{2x^{2}}\)

Possible Answers:

\(\displaystyle \frac{8x+4}{2x^{2}}\)

\(\displaystyle \frac{12x+8}{2x^{2}}\)

\(\displaystyle \frac{6x+4}{2x^{2}}\)

\(\displaystyle \frac{6x+2}{x^{2}}\)

\(\displaystyle \frac{6x+8}{2x^{2}}\)

Correct answer:

\(\displaystyle \frac{6x+2}{x^{2}}\)

Explanation:

Since both rational terms in the expression have the common denominator \(\displaystyle 2x^{2}\), combine the numerators and simplify like terms:

 

\(\displaystyle \frac{5x-5}{2x^{2}} + \frac{7x+9}{2x^{2}}\)

\(\displaystyle =\frac{(5x-5)+(7x+9)}{2x^{2}}\)

\(\displaystyle =\frac{12x+4}{2x^{2}}\)

\(\displaystyle =\frac{6x+2}{x^2}\)

Example Question #5 : How To Add Rational Expressions With A Common Denominator

 

 

Combine the following rational expressions:

\(\displaystyle \frac{3x^2-4x+5}{x+1}+\frac{4x^2-5x+9}{x+1}\)

Possible Answers:

\(\displaystyle \frac{7x^2 -9x+7}{x-1}\)

\(\displaystyle \frac{7x^2 +x+14}{x+1}\)

\(\displaystyle \frac{12x^2 +6x+15}{x+1}\)

\(\displaystyle \frac{-x^2 -9x+14}{x+1}\)

\(\displaystyle \frac{7x^2 -9x+14}{x+1}\)

Correct answer:

\(\displaystyle \frac{7x^2 -9x+14}{x+1}\)

Explanation:

When working with complex fractions, it is important not to let them intimidate you. They follow the same rules as regular fractions!

\(\displaystyle \frac{3x^2-4x+5}{x+1}+\frac{4x^2-5x+9}{x+1}\)

In this case, our problem is made easier by the fact that we already have a common denominator. Nothing fancy is required to start. Simply add the numerators:

\(\displaystyle \frac{(3x^2-4x+5)+(4x^2-5x+9)}{x+1}\)

For our next step, we need to combine like terms. This is easier to see if we group them together.

\(\displaystyle \frac{({\color{Blue} 3x^2+4x^2})+({\color{Red} -4x+-5x})+({\color{DarkOrange} 5+9})}{x+1}\)

\(\displaystyle \frac{({\color{Blue}7x^2})+({\color{Red} -9x})+({\color{DarkOrange} 14})}{x+1}\)

Thus, our final answer is:

\(\displaystyle \frac{7x^2 -9x+14}{x+1}\)

Example Question #2431 : Act Math

If x = y – 3, then (y – x)=

Possible Answers:

–27

27

3

–9

9

Correct answer:

27

Explanation:

Solve for equation for y – x = 3. Then, plug in 3 into (y – x)= 27.

Example Question #31 : Expressions

When graphed in the (x,y) coordinate plane, at what point do the lines -2x + 4y = 5 and y = -2 intersect? 

Possible Answers:

(13/2,-2)

(2,-2)

(-13/2,-2)

(13/2,2)

Correct answer:

(-13/2,-2)

Explanation:

Plugging in y=-2 in the second equation, gives x=-13/2. This is the point where the graphs intersect. 

Example Question #32 : Expressions

The length in cm of a plastic container is 5cm less than triple its width.  Which of the following equations is an accurate description of the length, l, as a function of the width, w?

Possible Answers:

l = 3w – 5

l = 1/3w – 5

l = 5/3w + 3/5

l = 3w + 5

l = 1/3w + 5

Correct answer:

l = 3w – 5

Explanation:

This problem requires the development of an equation.  We are told that the length is 5cm less than 3 times its width.  So we should set up an equation that describes this situation. The equation l = 3w – 5 demonstrates how the length is 5 cm less than 3 times the width of the container.

Example Question #3 : How To Evaluate Algebraic Expressions

The expression x(9 + x)(x – 2) = 4 is a polynomial of which degree?

Possible Answers:

1

3

4

0

2

Correct answer:

3

Explanation:

The highest power this polynomial can achieve is 3.

Example Question #5 : How To Evaluate Algebraic Expressions

Given that x = 2 and y = 3, how much less is the value of  3x2 – 2y than the value of  3y– 2x?

Possible Answers:

17

6

1

29

47

Correct answer:

17

Explanation:

First, we solve each expression by plugging in the given values for x and y:

3(22) – 2(3) = 12 – 6 = 6

3(32) – 2(2) = 27 – 4 = 23

Then we find the difference between the first and second expressions’ values:

23 – 6 = 17

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