Algebra II : Algebra II

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #91 : Solving Exponential Equations

Solve:  \displaystyle (\frac{1}{2})^{5x+2} =( \frac{1}{8})^{3x}

Possible Answers:

\displaystyle \frac{1}{2}

\displaystyle \frac{3}{2}

\displaystyle \frac{3}{4}

\displaystyle -2

Correct answer:

\displaystyle \frac{1}{2}

Explanation:

We can rewrite the right side by changing the base.

\displaystyle \frac{1}{8} = (\frac{1}{2})^3

Rewrite the right side using the new base.

\displaystyle (\frac{1}{2})^{5x+2} =[(\frac{1}{2})^3]^{3x}

Now that the bases are similar, we can set the exponents equal to each other.

\displaystyle 5x+2 = 9x

Subtract \displaystyle 5x on both sides.

\displaystyle 5x+2 -5x= 9x-5x

\displaystyle 2=4x

Divide by four on both sides.

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

Reduce the fractions.

The answer is:  \displaystyle \frac{1}{2}

Example Question #94 : Solving Exponential Equations

Solve the equation:  \displaystyle 3(\frac{1}{3})^{3x+1}= (\frac{1}{9})^{10}

Possible Answers:

\displaystyle \frac{40}{3}

\displaystyle \frac{19}{3}

\displaystyle 13

\displaystyle \frac{20}{3}

Correct answer:

\displaystyle \frac{20}{3}

Explanation:

We will need to convert the bases on both sides to base three.

\displaystyle \frac{1}{3} = 3^{-1}

\displaystyle \frac{1}{9}=(\frac{1}{3})^2

Rewrite the equation.

\displaystyle 3[(3)^{-1}]^{3x+1}= (3^{-2})^{10}

Simplify both sides.

\displaystyle 3(3)^{-1(3x+1)}= (3^{-2})^{10}

On the left side, notice that a lone three is the coefficient of the base.  We will need to write the left side such that:

\displaystyle 3(3)^{-1(3x+1)} = 3^1\cdot (3)^{-1(3x+1)} = 3^{1+(-1)(3x+1)}

Recall that if the powers of the same base are multiplied, the powers can be added.

Simplify the exponent.

\displaystyle 3^{1+(-1)(3x+1)} = 3^{1-3x-1} = 3^{-3x}

The equation becomes:  \displaystyle 3^{-3x} = 3^{-20}

Set the exponential terms equal to each other now that the bases are equal.

\displaystyle -3x=-20

Divide by negative three on both sides.

\displaystyle \frac{-3x}{-3}=\frac{-20}{-3}

The answer is:  \displaystyle \frac{20}{3}

Example Question #1211 : Mathematical Relationships And Basic Graphs

Solve:  \displaystyle 2^{3x+3} = 8^{-5x}

Possible Answers:

\displaystyle -\frac{2}{7}

\displaystyle -6

\displaystyle -\frac{1}{6}

\displaystyle \frac{2}{3}

\displaystyle -3

Correct answer:

\displaystyle -\frac{1}{6}

Explanation:

Change the base of the second term to base two.

\displaystyle 8=2^3

\displaystyle 2^{3x+3} =(2^3)^{-5x}

Simplify the right side by multiplying the exponents.

\displaystyle 2^{3x+3} =(2)^{-15x}

Now that the bases are common, the exponents can be set equal to each other.

\displaystyle 3x+3 = -15x

Subtract \displaystyle 3x from both sides.

\displaystyle 3x+3-3x = -15x-3x

\displaystyle 3=-18x

Divide by negative 18 on both sides.

\displaystyle \frac{3}{-18}=\frac{-18x}{-18}

The answer is:  \displaystyle -\frac{1}{6}

Example Question #741 : Exponents

Solve:  \displaystyle 4^6 = 2^{3x-3}

Possible Answers:

\displaystyle 7

\displaystyle \frac{1}{5}

\displaystyle 5

\displaystyle 10

\displaystyle -\frac{1}{2}

Correct answer:

\displaystyle 5

Explanation:

To evaluate this equation, we will need to change the base of the left side.

\displaystyle 4=2^2

Rewrite the equation.

\displaystyle (2^2)^6 = 2^{3x-3}

\displaystyle 2^{12}= 2^{3x-3}

Now that both bases are similar, we can set the exponents equal to each other.

\displaystyle 12=3x-3

Add 3 on both sides.

\displaystyle 12+3=3x-3+3

\displaystyle 15=3x

Divide by three on both sides.

The answer is:  \displaystyle 5

Example Question #101 : Solving And Graphing Exponential Equations

Solve the equation:  \displaystyle 2(\frac{1}{2})^{7x-1}= (\frac{1}{4})^{3x+2}

Possible Answers:

\displaystyle 6

\displaystyle \frac{2}{3}

\displaystyle \frac{1}{6}

\displaystyle 8

Correct answer:

\displaystyle 6

Explanation:

Rewrite both sides of the equation so that we have same bases.

\displaystyle 2(\frac{1}{2})^{7x-1}= (\frac{1}{4})^{3x+2}

\displaystyle 2=2^1

\displaystyle \frac{1}{2} = 2^{-1}

\displaystyle \frac{1}{4} = 2^{-2}

\displaystyle 2^1\cdot (2^{-1})^{7x-1}= (2^{-2})^{3x+2}

Simplify the exponents.

\displaystyle 2^1\cdot (2^{-7x+1})= 2^{-6x-4}

Add the exponents on the left side.

\displaystyle 2^{-7x+2}= 2^{-6x-4}

Now that both sides have same bases, we can set the exponential terms equal.

\displaystyle -7x+2 = -6x-4

Add \displaystyle 7x on both sides.

\displaystyle -7x+2+7x = -6x-4+7x

\displaystyle 2 = x-4

Add four on both sides.

\displaystyle 2 +4= x-4+4

The answer is:  \displaystyle 6

Example Question #741 : Exponents

Solve:  \displaystyle 3^4 = (\frac{1}{27})^{9x-3}

Possible Answers:

\displaystyle \frac{5}{3}

\displaystyle -\frac{2}{3}

\displaystyle \frac{5}{27}

\displaystyle -\frac{13}{27}

\displaystyle \frac{1}{9}

Correct answer:

\displaystyle \frac{5}{27}

Explanation:

In order to solve this, we will need to rewrite the fractional base to base three.

\displaystyle \frac{1}{27} = 3^{-3}

Rewrite the equation using this base.

\displaystyle 3^4 = (3^{-3})^{9x-3}

Now that both bases are common, we can set up an equation where the powers are equal.

\displaystyle 4=-3(9x-3)

Use distribution to simplify the right side.

\displaystyle 4=-27x+9

Subtract nine from both sides.

\displaystyle 4-9=-27x+9-9

\displaystyle -5 = -27x

Divide by negative 27 on both sides.

\displaystyle \frac{-5 }{-27}= \frac{-27x}{-27}

The answer is:  \displaystyle \frac{5}{27}

Example Question #101 : Solving And Graphing Exponential Equations

Evaluate:  \displaystyle (\frac{2}{3})^{3x-8} =( \frac{8}{27})^{-x-2}

Possible Answers:

\displaystyle -\frac{5}{3}

\displaystyle \frac{7}{3}

\displaystyle -\frac{1}{4}

\displaystyle \frac{1}{3}

\displaystyle \frac{2}{9}

Correct answer:

\displaystyle \frac{1}{3}

Explanation:

To solve this exponential equation, we will need to change the base of the second term.  Notice that both the numerator and denominator are the values of the left fraction cubed.  

\displaystyle \frac{8}{27} = (\frac{2}{3})^3

Rewrite the equation.

\displaystyle (\frac{2}{3})^{3x-8} =( \frac{2}{3})^{3(-x-2)}

With common bases, we can set the exponents equal to each other.

\displaystyle 3x-8 = 3(-x-2)

Distribute the right side.

\displaystyle 3x-8 = -3x-6

Add \displaystyle 3x on both sides.

\displaystyle 3x-8 +(3x)= -3x-6+(3x)

\displaystyle 6x-8 = -6

Add 8 on both sides.

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

\displaystyle 6x=2

Divide by six on both sides.

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

The answer is:  \displaystyle \frac{1}{3}

Example Question #91 : Solving Exponential Equations

Solve:  \displaystyle (\frac{1}{9}) ^{81} = 3^{2x-10}

Possible Answers:

\displaystyle -86

\displaystyle 86

\displaystyle -152

\displaystyle -76

Correct answer:

\displaystyle -76

Explanation:

In order to solve this equation, we will need to change the base of the left side.

Rewrite one-ninth as base three.

\displaystyle \frac{1}{9} = 3^{-2}

Rewrite the equation.

\displaystyle (3^{-2}) ^{81} = 3^{2x-10}

Now that both bases are common, we can set both powers equal.

\displaystyle (-2)(81) = 2x-10

Simplify the left side and solve for x.

\displaystyle -162 = 2x-10

Add 10 on both sides, and then divide by two.

\displaystyle -162 +10= 2x-10+10

\displaystyle \frac{-152}{2}=\frac{2x}{2}

The answer is:  \displaystyle -76

Example Question #1212 : Mathematical Relationships And Basic Graphs

Solve:  \displaystyle 2^{5x+2} = (\frac{1}{2})^{10x+3}

Possible Answers:

\displaystyle \frac{1}{15}

\displaystyle -\frac{1}{6}

\displaystyle -\frac{1}{9}

\displaystyle -\frac{1}{3}

\displaystyle \frac{1}{12}

Correct answer:

\displaystyle -\frac{1}{3}

Explanation:

Change the base of the right side.

\displaystyle \frac{1}{2} =2^{-1}

Rewrite the base of the right side.

\displaystyle 2^{5x+2} = (2^{-1})^{10x+3}

Set the exponents equal to each other now that both of the bases are alike.

\displaystyle 5x+2 = -1(10x+3)

Simplify both sides.

\displaystyle 5x+2 = -10x-3

Add \displaystyle 10x on both sides.

\displaystyle 5x+2 +10x= -10x-3+10x

\displaystyle 15x+2= -3

Subtract two on both sides.

\displaystyle 15x+2-2= -3-2

\displaystyle 15x=-5

Divide by 15 on both sides.

\displaystyle \frac{15x}{15}=\frac{-5}{15}

Reduce both fractions.

The answer is:  \displaystyle -\frac{1}{3}

Example Question #102 : Solving Exponential Equations

Solve the equation:  \displaystyle 8^{10x} = 8^{-9x-19}

Possible Answers:

\displaystyle -1

\displaystyle 1

\displaystyle \frac{19}{8}

\displaystyle 0

Correct answer:

\displaystyle -1

Explanation:

The bases on both sides of the equation are equal.  This means we can set the powers equal to each other.

\displaystyle 10x= -9x-19

Add \displaystyle 9x on both sides.

\displaystyle 10x+9x= -9x-19+9x

\displaystyle 19x = -19

Divide by 19 on both sides.

\displaystyle \frac{19x}{19} = \frac{-19}{19}

The answer is:  \displaystyle -1

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