SAT II Math II : Single-Variable Algebra

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

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Example Questions

Example Question #1 : Solving Equations

Solve the equation for y

\displaystyle 5y+27-5z=30

Possible Answers:

\displaystyle y=3+5z

\displaystyle 5y=3+5z

\displaystyle z=\frac{3-5y}{5}

\displaystyle 5y-5z=3

\displaystyle y=\frac{3+5z}{5}

Correct answer:

\displaystyle y=\frac{3+5z}{5}

Explanation:

\displaystyle 5y+27-5z=30

First subtract 27 from both sides of the equation

\displaystyle 5y-5z=3

Add 5z to both sides of the equation

\displaystyle 5y=3+5z

Lastly, divide both sides by 5 to get the y by itself

\displaystyle y=\frac{3+5z}{5}

Example Question #2 : Solving Equations

Solve the equation:  \displaystyle \frac{2}{3x}+4=\frac{1}{2x}

Possible Answers:

\displaystyle \frac{1}{24}

\displaystyle \frac{1}{48}

\displaystyle -\frac{1}{12}

\displaystyle -\frac{1}{24}

\displaystyle \frac{1}{12}

Correct answer:

\displaystyle -\frac{1}{24}

Explanation:

To isolate the x-variable, we can multiply both sides by the least common denominator.

The least common denominator is \displaystyle 6x.  This will eliminate the fractions.

\displaystyle 6x(\frac{2}{3x}+4)=\frac{1}{2x} \cdot 6x

\displaystyle 4+24x = 3

Subtract 4 on both sides.

\displaystyle 4+24x -4= 3-4

\displaystyle 24x=-1

Divide by 24 on both sides.

\displaystyle \frac{24x}{24}=\frac{-1}{24}

The answer is:  \displaystyle -\frac{1}{24}

Example Question #161 : Sat Subject Test In Math Ii

Solve the equation:  \displaystyle \frac{1}{3}x-\frac{1}{4}x = \frac{1}{5}

Possible Answers:

\displaystyle \frac{10}{3}

\displaystyle \frac{24}{5}

\displaystyle \frac{7}{60}

\displaystyle \frac{12}{5}

\displaystyle \frac{13}{60}

Correct answer:

\displaystyle \frac{12}{5}

Explanation:

Find the least common denominator of both sides of the equation, and multiply it on both sides.  

The LCD is 60.

\displaystyle 60(\frac{1}{3}x-\frac{1}{4}x) = \frac{1}{5}\times 60

\displaystyle 20x-15x = 12

Combine like-terms on the left.

\displaystyle 5x=12

Divide by 5 on both sides.

\displaystyle \frac{5x}{5}=\frac{12}{5}

The answer is:  \displaystyle \frac{12}{5}

Example Question #2 : Solving Equations

Solve the equation:  \displaystyle 8(x-3) = 16-x

Possible Answers:

\displaystyle \frac{40}{9}

\displaystyle \frac{40}{7}

\displaystyle \frac{8}{9}

\displaystyle 2

\displaystyle 3

Correct answer:

\displaystyle \frac{40}{9}

Explanation:

Distribute the eight through both terms of the binomial.

\displaystyle 8x-24 = 16-x

Add \displaystyle x on both sides.

\displaystyle 8x-24 +x= 16-x+x

\displaystyle 9x-24 = 16

Add 24 on both sides.

\displaystyle 9x-24+24 = 16+24

\displaystyle 9x=40

Divide by 9 on both sides.

\displaystyle \frac{9x}{9}=\frac{40}{9}

The answer is:  \displaystyle \frac{40}{9}

Example Question #1 : Solving Equations

Solve the equation:  \displaystyle -2+7x = 8x-6

Possible Answers:

\displaystyle 4

\displaystyle -8

\displaystyle -\frac{4}{15}

\displaystyle \frac{4}{15}

\displaystyle -\frac{8}{15}

Correct answer:

\displaystyle 4

Explanation:

Subtract \displaystyle 7x from both sides.

\displaystyle -2+7x-7x = 8x-6-7x

\displaystyle -2=x-6

Add 6 on both sides.

\displaystyle -2+6=x-6+6

\displaystyle x=4

The answer is:  \displaystyle 4

Example Question #1 : Solving Equations

Solve \displaystyle \sqrt{x^2 + 8} = 2\sqrt{2x-1}

Possible Answers:

\displaystyle x=7

\displaystyle x=-3, 6

\displaystyle x=2, 6

\displaystyle x= \sqrt{3}, \sqrt{6}

\displaystyle x=3, 9

Correct answer:

\displaystyle x=2, 6

Explanation:

First, we want to get everything inside the square roots, so we distribute the \displaystyle 2:

\displaystyle \sqrt{x^2 + 8} = \sqrt{4}\sqrt{2x-1}

\displaystyle \sqrt{x^2 + 8} = \sqrt{4(2x-1)}

\displaystyle \sqrt{x^2 + 8} = \sqrt{8x-4}

Now we can clear our the square roots by squaring each side:

\displaystyle (\sqrt{x^2 + 8})^{2} = (\sqrt{8x-4})^2

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

Now we can simplify by moving everything to one side of the equation:

\displaystyle x^2 -8x+ 12 = 0

Factoring will give us:

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

So our answers are:

\displaystyle x=2, 6

Example Question #2 : Solving Equations

Solve \displaystyle 6-\sqrt{x}=11

Possible Answers:

\displaystyle -25

No solution.

\displaystyle 5

\displaystyle 25

\displaystyle -5

Correct answer:

No solution.

Explanation:

Begin by gathering all the constants to one side of the equation:

\displaystyle -\sqrt{x}=5

Now multiply by \displaystyle -1:

\displaystyle \sqrt{x}=-5

And finally, square each side:

\displaystyle x=25

This might look all fine and dandy, but let's check our solution by plugging it in to the original equation:

\displaystyle 6-\sqrt{25}=11

\displaystyle 6-5=11

\displaystyle 1\neq 11

So our solution is invalid, and the problem doesn't have a solution.

Example Question #162 : Sat Subject Test In Math Ii

Solve the equation:  \displaystyle 3x-2 = 50

Possible Answers:

\displaystyle 55

\displaystyle 16

\displaystyle 17

\displaystyle \frac{52}{3}

\displaystyle 48

Correct answer:

\displaystyle \frac{52}{3}

Explanation:

Add two on both sides.

\displaystyle 3x-2+2 = 50+2

\displaystyle 3x = 52

Divide by three on both sides.

\displaystyle \frac{3x }{3}=\frac{ 52}{3}

The answer is:  \displaystyle \frac{52}{3}

Example Question #11 : Solving Equations

Solve:  \displaystyle \frac{2}{3}x = \frac{5}{2}

Possible Answers:

\displaystyle \frac{10}{3}

\displaystyle \frac{4}{15}

\displaystyle \frac{3}{5}

\displaystyle \frac{5}{3}

\displaystyle \frac{15}{4}

Correct answer:

\displaystyle \frac{15}{4}

Explanation:

To isolate the x-variable, multiply both sides by the coefficient of the x-variable.

\displaystyle \frac{2}{3}x \cdot \frac{3}{2} = \frac{5}{2}\cdot\frac{3}{2}

The answer is:  \displaystyle \frac{15}{4}

Example Question #12 : Solving Equations

Give the solution set of the following rational equation:

\displaystyle \frac{ x^{2}-4x}{x^{2}-2x} = 2

Possible Answers:

No solution

\displaystyle \left \{ 2, 4 \right \}

\displaystyle \left \{ 0, 4 \right \}

\displaystyle \left \{ 0, 2, 4 \right \}

\displaystyle \left \{ 0\right \}

Correct answer:

No solution

Explanation:

Multiply both sides of the equation by \displaystyle x^{2}-2x to eliminate the fraction:

\displaystyle \frac{ x^{2}-4x}{x^{2}-2x} = 2

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

\displaystyle x^{2}-4x = 2 x^{2}-4x

Subtract \displaystyle x^{2}-4x from both sides:

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

\displaystyle 2 x^{2} - x^{2} -4x + 4x = 0

\displaystyle x^{2} = 0

The only possible solution is \displaystyle x = 0, However, if this is substituted in the original equation, the expression at left is undefined, as seen here:

\displaystyle \frac{ x^{2}-4x}{x^{2}-2x} = 2

\displaystyle \frac{ 0^{2}-4 \cdot 0}{0^{2}-2 \cdot 0} = 2

\displaystyle \frac{ 0}{ 0} = 2

An expression with a denominator of 0 has an undefined value, so this statement is false. The equation has no solution.

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