ACT Math : Squaring / Square Roots / Radicals

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #2 : Square Of Sum

Which of the following is the square of \(\displaystyle 3.7x + 1.4 y\) ? 

Possible Answers:

\(\displaystyle 7.4x^{2}+ 5.18x y +2.8 y ^{2}\)

\(\displaystyle 13.69x^{2}+ 5.18x y +1.96 y ^{2}\)

\(\displaystyle 7.4x^{2}+ 10.36x y +2.8 y ^{2}\)

\(\displaystyle 13.69x^{2}+ 10.36x y +1.96 y ^{2}\)

\(\displaystyle 13.69x^{2} +1.96 y ^{2}\)

Correct answer:

\(\displaystyle 13.69x^{2}+ 10.36x y +1.96 y ^{2}\)

Explanation:

Use the square of a sum pattern, substituting \(\displaystyle 3.7x\) for \(\displaystyle A\) and \(\displaystyle 1.4 y\) for \(\displaystyle B\) in the pattern:

\(\displaystyle (A+ B)^{2}= A^{2}+ 2AB + B^{2}\)

\(\displaystyle \left (3.7x + 1.4 y \right )^{2}= (3.7x)^{2}+ 2 (3.7x)(1.4 y) + (1.4 y) ^{2}\)

\(\displaystyle = 13.69x^{2}+ 10.36x y +1.96 y ^{2}\)

Example Question #1 : Factoring Squares

Which real number satisfies \(\displaystyle 3^{x}*9=27^{2}\)?

 

Possible Answers:

\(\displaystyle 3\)

\(\displaystyle 2\)

\(\displaystyle 1\)

\(\displaystyle 4\)

\(\displaystyle 5\)

Correct answer:

\(\displaystyle 4\)

Explanation:

Simplify the base of 9 and 27 in order to have a common base.

(3x)(9)=272

= (3x)(32)=(33)2

=(3x+2)=36

Therefore:

x+2=6

x=4

 

 

Example Question #2 : Factoring Squares

Which of the following is a factor of \(\displaystyle 4x^{4}+ 36 x^{2}\) ?

Possible Answers:

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

\(\displaystyle 2x^{2}+ 9\)

\(\displaystyle x^{2}+ 9\)

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

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

Correct answer:

\(\displaystyle x^{2}+ 9\)

Explanation:

The terms of \(\displaystyle 4x^{4}+ 36 x^{2}\) have \(\displaystyle 4x^{2}\) as their greatest common factor, so

\(\displaystyle 4x^{4}+ 36 x^{2} = 4x^{2} (x^{2}+9)\)

\(\displaystyle x^{2}+ 9\) is a prime polynomial. 

Of the five choices, only \(\displaystyle x^{2}+ 9\) is a factor.

Example Question #2 : Factoring Squares

Simplify \(\displaystyle \frac{8^{3} \times 3}{2^{6}\times 27}\) 

Possible Answers:

\(\displaystyle \frac{16}{9}\)

\(\displaystyle \frac{32}{9}\)

\(\displaystyle \frac{9}{8}\)

\(\displaystyle \frac{8}{9}\)

\(\displaystyle \frac{4}{3}\)

Correct answer:

\(\displaystyle \frac{8}{9}\)

Explanation:

The easiest way to approach this problem is to break everything into exponents. \(\displaystyle 8^{3}\) is equal to \(\displaystyle 2^{9}\) and 27 is equal to \(\displaystyle 3^{3}\). Therefore, the expression can be broken down into \(\displaystyle \frac{2^{9} \times 3}{2^{6}\times 3^{3}}\). When you cancel out all the terms, you get \(\displaystyle \frac{2^{3}}{3^{2}}\), which equals \(\displaystyle \frac{8}{9}\).

Example Question #2361 : Sat Mathematics

Which of the following expression is equal to

\(\displaystyle \sqrt{(45)(9)+(27)(36)}\)

 

Possible Answers:

\(\displaystyle 9\sqrt{15}\)

\(\displaystyle 9\sqrt{19}\)

\(\displaystyle 9\sqrt{17}\)

\(\displaystyle 7\sqrt{17}\)

\(\displaystyle 7\sqrt{15}\)

Correct answer:

\(\displaystyle 9\sqrt{17}\)

Explanation:

\(\displaystyle \sqrt{(45)(9)+(27)(36)}\)

When simplifying a square root, consider the factors of each of its component parts:

\(\displaystyle \sqrt{(3^2)\times5\times(3^{2})+(3^{3})(2^2)(3^2)}\)

Combine like terms:

\(\displaystyle \sqrt{5(3^4)+(2^2)(3^5)}\)

Remove the common factor, \(\displaystyle 3^4\):

\(\displaystyle \sqrt{(3^4)\times(5+3\times(2^2))}\)

Pull the \(\displaystyle \sqrt{3^4}\) outside of the equation as \(\displaystyle 3^2\):

\(\displaystyle (3^2)\sqrt{5+12}=9\sqrt{17}\)                       

Example Question #2 : How To Factor A Common Factor Out Of Squares

Which of the following is equal to the following expression?

\(\displaystyle \sqrt{(16)(8)+(32)(20)}\)

Possible Answers:

\(\displaystyle 2^{4}\sqrt{5}\)

\(\displaystyle 2^{7}\sqrt{5}\)

\(\displaystyle 2^4\sqrt{3}\)

\(\displaystyle 2^{3}\sqrt{10}\)

\(\displaystyle 2^{3}\sqrt{6}\)

Correct answer:

\(\displaystyle 2^4\sqrt{3}\)

Explanation:

\(\displaystyle \sqrt{(16)(8)+(32)(20)}\)

First, break down the components of the square root:

\(\displaystyle \sqrt{(2^{4})(2^{3})+(2^{5})(2^{2})\times 5}\)

Combine like terms. Remember, when multiplying exponents, add them together:

\(\displaystyle \sqrt{(2^{7})+(2^{7})\times5}\)

Factor out the common factor of \(\displaystyle 2^7\):

\(\displaystyle \sqrt{(2^{7})(1+5)}\)

\(\displaystyle \sqrt{(2^7)\times6}\)

Factor the \(\displaystyle 6\):

\(\displaystyle \sqrt{(2^7)\times2\times3}\)

Combine the factored \(\displaystyle 2\) with the \(\displaystyle 2^7\):

\(\displaystyle \sqrt{(2^{8})\times3}\)

Now, you can pull \(\displaystyle \sqrt{2^8}\) out from underneath the square root sign as \(\displaystyle 2^4\):

\(\displaystyle 2^4\sqrt{3}\)

Example Question #4 : Squaring / Square Roots / Radicals

Which of the following expressions is equal to the following expression?

\(\displaystyle \sqrt{(27)(45)(125)}\)

Possible Answers:

\(\displaystyle 125\sqrt{27}\)

\(\displaystyle 205\sqrt{3}\)

\(\displaystyle 135\sqrt{5}\)

\(\displaystyle 225\sqrt{3}\)

\(\displaystyle 75\sqrt{20}\)

Correct answer:

\(\displaystyle 225\sqrt{3}\)

Explanation:

\(\displaystyle \sqrt{(27)(45)(125)}\)

First, break down the component parts of the square root:

\(\displaystyle \sqrt{(3^{3})(5\times 3^{2})(5^{3})}\)

Combine like terms in a way that will let you pull some of them out from underneath the square root symbol:

\(\displaystyle \sqrt{(5^{4})(3^4)(3)}\)

Pull out the terms with even exponents and simplify:

\(\displaystyle (5^{2})(3^{2})\sqrt{3}=225\sqrt{3}\)

Example Question #12 : Squaring / Square Roots / Radicals

What is,

 \(\displaystyle \frac{12}{\sqrt{18}}\)?

Possible Answers:

\(\displaystyle 3*\sqrt{3}\)

\(\displaystyle 3*\sqrt{2}\)

\(\displaystyle 2*\sqrt{2}\)

\(\displaystyle 4*\sqrt{3}\)

\(\displaystyle 2*\sqrt{3}\)

Correct answer:

\(\displaystyle 2*\sqrt{2}\)

Explanation:

To find an equivalency we must rationalize the denominator.

To rationalize the denominator multiply the numerator and denominator by the denominator.

\(\displaystyle \frac{12}{\sqrt{18}}*\frac{\sqrt{18}}{\sqrt{18}}=\) 

\(\displaystyle \frac{12*\sqrt{18}}{18}=\)

Factor out 6,

 \(\displaystyle \frac{2*\sqrt{18}}{3}=\)

Extract perfect square 9 from the square root of 18.

\(\displaystyle \sqrt{18}=3*\sqrt{2}\)

\(\displaystyle \frac{2*3*\sqrt{2}}{3}=\) 

\(\displaystyle 2*\sqrt{2}\)

Example Question #831 : Algebra

Subtract \(\displaystyle a\) from \(\displaystyle b\), given:

\(\displaystyle a = 3 + i\)

\(\displaystyle b = 4 - 2i\)

Possible Answers:

\(\displaystyle 3 + i\)

\(\displaystyle 1 - 3i\)

\(\displaystyle -1 + 3i\)

\(\displaystyle -1 - 3i\)

\(\displaystyle 1+ 3i\)

Correct answer:

\(\displaystyle 1 - 3i\)

Explanation:

A complex number is a combination of a real and imaginary number. To subtract complex numbers, subtract each element separately.

In equation \(\displaystyle a\)\(\displaystyle 3\) is the real component and \(\displaystyle 1\) is the imaginary component (designated by \(\displaystyle i\)). In equation \(\displaystyle b\)\(\displaystyle 4\) is the real component and \(\displaystyle -2\) is the imaginary component. Solving for \(\displaystyle b - a\),

\(\displaystyle b-a = \left ( 4-2i\right ) - \left ( 3 + i\right ) = \left ( 4-3\right ) + i\left ( -2-1\right ) = 1 - 3i\)

Example Question #2 : How To Subtract Complex Numbers

Simplify the exponent,

\(\displaystyle (3^{6})^{2}\).

Possible Answers:

\(\displaystyle 3^{12}\)

\(\displaystyle 3^{4}\)

\(\displaystyle 3^{8}\)

\(\displaystyle 3^{3}\)

Correct answer:

\(\displaystyle 3^{12}\)

Explanation:

When you have an exponent on the outside of parentheses while another is on the inside of the parentheses, such as in \(\displaystyle (3^{6})^{2}\), multiply the exponents together to get the answer: \(\displaystyle 3^{12}\).

 

This is different than when you have two numbers with the same base multiplied together, such as in \(\displaystyle x^{2} \cdot x^{3} = x^{5}\). In that case, you add the exponents together.

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