SAT II Math II : Simplifying Expressions

Study concepts, example questions & explanations for SAT II Math II

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Example Questions

Example Question #1 : Simplifying Expressions

Decrease \(\displaystyle 8d - 35\) by 40%. Which of the following will this be equal to?

Possible Answers:

\(\displaystyle 4.8 d - 21\)

\(\displaystyle 3.2d - 14\)

\(\displaystyle 4.8d-35\)

\(\displaystyle 8d-21\)

\(\displaystyle 3.2d-21\)

Correct answer:

\(\displaystyle 4.8 d - 21\)

Explanation:

A number decreased by 40% is equivalent to 100% of the number minus 40% of the number. This is taking 60% of the number, or, equivalently, multiplying it by 0.6. 

Therefore, \(\displaystyle 8d - 35\) decreased by 40% is 0.6 times this, or

\(\displaystyle 0.6 \left (8d - 35 \right ) = 0.6 \cdot 8d - 0.6 \cdot 35 = 4.8 d - 21\)

Example Question #2 : Simplifying Expressions

Simplify:

\(\displaystyle \left ( 3x^{-3}\right )^{-3}\)

Possible Answers:

\(\displaystyle 27x^{9}\)

\(\displaystyle -27x^{9}\)

\(\displaystyle \frac{ x^{9} }{27}\)

\(\displaystyle \frac{1}{27x^{9}}\)

\(\displaystyle \frac{27}{ x^{9} }\)

Correct answer:

\(\displaystyle \frac{ x^{9} }{27}\)

Explanation:

\(\displaystyle \left ( 3x^{-3}\right )^{-3}\)

\(\displaystyle = \left ( \frac{3}{x^{3}}\right )^{-3}\)

\(\displaystyle = \left ( \frac{x^{3}}{3}\right )^{3}\)

\(\displaystyle = \frac{\left (x^{3} \right )^{3}}{3^{3}}\)

\(\displaystyle = \frac{ x^{3 \cdot 3} }{27}\)

\(\displaystyle = \frac{ x^{9} }{27}\)

Example Question #1 : Simplifying Expressions

Assume all variables assume positive values.

Simplify:

\(\displaystyle \left ( \frac{y^{-3}}{x^{-2}} \right )^{2}\)

Possible Answers:

\(\displaystyle \frac{x^{4}}{y^{6}}\)

\(\displaystyle \frac{y^{6}}{x^{4}}\)

\(\displaystyle \frac{x^{4}}{y^{9}}\)

\(\displaystyle \frac{1}{x^{4}y^{6}}\)

\(\displaystyle \frac{y^{9}}{x^{4}}\)

Correct answer:

\(\displaystyle \frac{x^{4}}{y^{6}}\)

Explanation:

\(\displaystyle \left ( \frac{y^{-3}}{x^{-2}} \right )^{2}\)

\(\displaystyle = \frac{y^{-3 \cdot 2}}{x^{-2\cdot 2}}\)

\(\displaystyle = \frac{y^{-6}}{x^{-4}}\)

\(\displaystyle = y^{-6} \div x^{-4}\)

\(\displaystyle = \frac{1}{y^{6}} \div \frac{1}{ x^{4}}\)

\(\displaystyle = \frac{1}{y^{6}} \cdot x^{4}\)

\(\displaystyle = \frac{x^{4}}{y^{6}}\)

Example Question #1 : Simplifying Expressions

Assume all variables assume positive values. Simplify:

\(\displaystyle 6x^{0}+ 7y^{0}+ 8z^{0}\)

Possible Answers:

The expression is already simplified.

\(\displaystyle 21xyz\)

The expression is undefined.

\(\displaystyle 6x + 7y + 8z\)

\(\displaystyle 21\)

Correct answer:

\(\displaystyle 21\)

Explanation:

Any nonzero expression raised to the power of 0 is equal to 1. Therefore, 

\(\displaystyle 6x^{0}+ 7y^{0}+ 8z^{0}\)

\(\displaystyle = 6 \cdot 1 + 7 \cdot 1 + 8 \cdot 1\)

\(\displaystyle = 6 + 7 + 8 = 21\)

Example Question #192 : Sat Subject Test In Math Ii

Simplify the following expression:  \(\displaystyle xyz(xy-xz)\)

Possible Answers:

\(\displaystyle x^2y^2z^2-x^2yz^2\)

\(\displaystyle 2xyz-2xz\)

\(\displaystyle x^2y^2z-x^2yz^2\)

\(\displaystyle x^2y^2z-x^2yz\)

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

Correct answer:

\(\displaystyle x^2y^2z-x^2yz^2\)

Explanation:

Distribute the outer term through both terms in the parentheses.

\(\displaystyle xyz(xy-xz) = xyz(xy) - xyz(xz)\)

Multiply each term.

\(\displaystyle x^2y^2z-x^2yz^2\)

There are no like-terms.

The answer is:  \(\displaystyle x^2y^2z-x^2yz^2\)

Example Question #2 : Simplifying Expressions

Simplify the expression:  \(\displaystyle 6(2x-3)-2(-x-3)\)

Possible Answers:

\(\displaystyle 10x+9\)

\(\displaystyle 12x-12\)

\(\displaystyle 14x-24\)

\(\displaystyle 10x-9\)

\(\displaystyle 14x-12\)

Correct answer:

\(\displaystyle 14x-12\)

Explanation:

Distribute the integers through the binomials.

\(\displaystyle 12x-18 +2x+6\)

Combine like-terms.

The answer is:  \(\displaystyle 14x-12\)

Example Question #3 : Simplifying Expressions

Simplify \(\displaystyle x - 5 - (2 - x)\).

Possible Answers:

\(\displaystyle 2x - 7\)

\(\displaystyle 0\)

\(\displaystyle x^2 - 7\)

\(\displaystyle x+3\)

\(\displaystyle -3\)

Correct answer:

\(\displaystyle 2x - 7\)

Explanation:

We can start by distributing the negative sign in the parentheses term:

\(\displaystyle x - 5 - 2 + x\)

Now we can combine like terms.  The constants go together, and the variables go together:

\(\displaystyle 2x - 7\)

Example Question #3 : Simplifying Expressions

Simplify \(\displaystyle -(x + y) + 4x + 2y\).

Possible Answers:

\(\displaystyle 3x + y\)

\(\displaystyle 3x-y\)

\(\displaystyle 3xy\)

\(\displaystyle 3(x+y)\)

\(\displaystyle 5x+3y\)

Correct answer:

\(\displaystyle 3x + y\)

Explanation:

First, we can distribute the negative sign through the parentheses term:

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

Now we gather like terms.  Remember, you can't gather different variables together.  The \(\displaystyle x\)'s and \(\displaystyle y\)'s will still be separate terms:

\(\displaystyle 3x + y\)

Example Question #4 : Simplifying Expressions

Simplify \(\displaystyle -(x + 2y + 3) - 3x + y\).

Possible Answers:

\(\displaystyle 2x +3y +3\)

\(\displaystyle 4x +y +3\)

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

\(\displaystyle -4x - y - 3\)

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

Correct answer:

\(\displaystyle -4x - y - 3\)

Explanation:

Start by distributing the negative sign through the parentheses term:

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

Now combine like terms.  Each variable can't be combined with different variables:

\(\displaystyle -4x - y - 3\)

Example Question #5 : Simplifying Expressions

Simplify \(\displaystyle (\sqrt{x^2})^2\)

Possible Answers:

\(\displaystyle x^2\)

\(\displaystyle \sqrt{x^3}\)

\(\displaystyle x^{\frac{1}{4}}\)

\(\displaystyle \sqrt{x^4}\)

\(\displaystyle x\)

Correct answer:

\(\displaystyle x^2\)

Explanation:

A square root is the inverse of squaring a term, so they cancel each other out:

\(\displaystyle (\sqrt{x^2})^2=x^2\)

From there, there's nothing left to simplify.

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