High School Math : Exponents

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #41 : Exponents

\(\displaystyle y=\frac{4x^2-2}{2x^3-27}\)

What are the x-intercepts of the equation?

Possible Answers:

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

\(\displaystyle x=\sqrt{2}, -\sqrt{2}\)

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

\(\displaystyle x=\frac{1}{\sqrt{2}}\)

\(\displaystyle x=\frac{\sqrt{2}}{2}, -\frac{\sqrt{2}}{2}\)

Correct answer:

\(\displaystyle x=\frac{\sqrt{2}}{2}, -\frac{\sqrt{2}}{2}\)

Explanation:

To find the x-intercepts, set the numerator equal to zero and solve.

\(\displaystyle 0=4x^2-2\)

\(\displaystyle 2=4x^2\)

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

\(\displaystyle \frac{1}{2}=x^2\)

\(\displaystyle \sqrt{\frac{1}{2}}=\sqrt{x^2}\)

We can simplify from here:

\(\displaystyle \frac{\sqrt1}{\sqrt2}}=\sqrt{x^2}\)

\(\displaystyle \frac{1}{\sqrt2}}=\sqrt{x^2}\)

Now we need to rationalize. Because we have a square root on the bottom, we need to get rid of it. Since \(\displaystyle 2=\sqrt{2}^2\), we can multiply \(\displaystyle \frac{1}{\sqrt2}*\frac{\sqrt{2}}{\sqrt{2}}\) to get rid of the radical in the denominator.

\(\displaystyle \frac{1}{\sqrt2}*\frac{\sqrt{2}}{\sqrt{2}}=x\)

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

Since we took a square root, remember that our answer can be either positive or negative, as a positive squared is positive and a negative squared is also positive.

Example Question #42 : Exponents

\(\displaystyle y=\frac{x-3}{x^2-12}\)

What are the y-intercepts of this equation?

Possible Answers:

\(\displaystyle y=0\)

\(\displaystyle y=4\)

\(\displaystyle y=\frac{1}{4}\)

\(\displaystyle y=2\sqrt{3}\)

There are no y-intercepts.

Correct answer:

\(\displaystyle y=\frac{1}{4}\)

Explanation:

To find the y-intercept, set \(\displaystyle x=0\) and solve.

\(\displaystyle y=\frac{x-3}{x^2-12}\)

\(\displaystyle y=\frac{(0)-3}{(0)^2-12}\)

\(\displaystyle y=\frac{-3}{-12}\)

\(\displaystyle y=\frac{1}{4}\)

Example Question #123 : Mathematical Relationships And Basic Graphs

\(\displaystyle y=\frac{x^2-64}{x+2}\)

What are the y-intercepts of this equation?

Possible Answers:

There are no y-intercepts for the equation.

\(\displaystyle y=-2\)

\(\displaystyle y=-32\)

\(\displaystyle y=0\)

\(\displaystyle y=32\)

Correct answer:

\(\displaystyle y=-32\)

Explanation:

To find the y-intercept, set \(\displaystyle x=0\) and solve.

\(\displaystyle y=\frac{x^2-64}{x+2}\)

\(\displaystyle y=\frac{(0)^2-64}{0+2}\)

\(\displaystyle y=\frac{-64}{2}\)

\(\displaystyle y=-32\)

Example Question #12 : Solving Exponential Equations

\(\displaystyle y=\frac{3x^2-5}{2x^2+7}\)

What are the x-intercepts of the equation?

Possible Answers:

\(\displaystyle x=\sqrt{\frac{5}{3}}\)

\(\displaystyle x=1\)

\(\displaystyle x=\sqrt{\frac{5}{3}}, -\sqrt{\frac{5}{3}}\)

\(\displaystyle x=0\)

There are no horizontal asymptotes.

Correct answer:

\(\displaystyle x=\sqrt{\frac{5}{3}}, -\sqrt{\frac{5}{3}}\)

Explanation:

To find the x-intercepts, we set the numerator equal to zero and solve.

\(\displaystyle 0=3x^2-5\)

\(\displaystyle 5=3x^2\)

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

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

\(\displaystyle \sqrt{\frac{5}{3}}=x\)

However, the square root of a number can be both positive and negative.

Therefore the roots will be \(\displaystyle x=\sqrt{\frac{5}{3}}, -\sqrt{\frac{5}{3}}.\)

Example Question #44 : Exponents

\(\displaystyle y=\frac{x^2-64}{x+2}\)

What are the x-intercepts of the equation?

Possible Answers:

There are no x-intercepts.

There are no real x-intercepts.

\(\displaystyle x=0\)

\(\displaystyle x=-2\)

\(\displaystyle x=8, -8\)

Correct answer:

\(\displaystyle x=8, -8\)

Explanation:

To find the x-intercepts, set the numerator equal to zero.

\(\displaystyle 0=x^2-64\)

\(\displaystyle 64=x^2\)

\(\displaystyle \sqrt{64}=\sqrt{x^2}\)

\(\displaystyle 8,-8=x\)

Example Question #1 : Solving Exponential Equations

Solve the equation for \(\displaystyle x\).

\(\displaystyle \small 9^x=3^6\)

Possible Answers:

\(\displaystyle \small x=1\)

\(\displaystyle \small x=3\)

\(\displaystyle \small x=2\)

\(\displaystyle \small x=0\)

Correct answer:

\(\displaystyle \small x=3\)

Explanation:

Begin by recognizing that both sides of the equation have a root term of \(\displaystyle 3\).

\(\displaystyle \small 9^x=3^6\)

\(\displaystyle (3^2)^x=3^6\)

Using the power rule, we can set the exponents equal to each other.

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

\(\displaystyle \small 2x=6\)

\(\displaystyle \small x=3\)

Example Question #141 : Algebra Ii

The population of a certain bacteria increases exponentially according to the following equation:

\(\displaystyle P(t)=2000e^{^{2t}}\)

where P represents the total population and t represents time in minutes.

How many minutes does it take for the bacteria's population to reach 48,000?

Possible Answers:

\(\displaystyle \frac{\log 24}{2}\)

\(\displaystyle \frac{2}{\ln 24}\)

\(\displaystyle \frac{\ln24}{2}\)

\(\displaystyle \ln 12\)

\(\displaystyle \frac{2}{\log 24}\)

Correct answer:

\(\displaystyle \frac{\ln24}{2}\)

Explanation:

The question gives us P (48,000) and asks us to find t (time). We can substitute for P and start to solve for t:

\(\displaystyle 48,000 = 2000e^{2t}\)

\(\displaystyle 24 = e^{2t}\)

Now we have to isolate t by taking the natural log of both sides:

\(\displaystyle \ln 24 = \ln e^{2t}\)

\(\displaystyle \ln 24 = (2t)\ln e\)

And since \(\displaystyle \ln e = 1\), t can easily be isolated:

\(\displaystyle \ln 24 = 2t\)

\(\displaystyle \frac{\ln24}{2} = t\)

Note: \(\displaystyle \frac{\ln 24}{2}\) does not equal \(\displaystyle \ln 12\) . You have to perform the log operation first before dividing.

Example Question #2 : Solving Exponential Equations

Solve the equation for \(\displaystyle x\).

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

Possible Answers:

\(\displaystyle x=2\)

 

\(\displaystyle x=1\)

 

 

 

\(\displaystyle x=9\)

\(\displaystyle x=3\)

\(\displaystyle x=4\)

Correct answer:

\(\displaystyle x=2\)

 

Explanation:

Begin by recognizing that both sides of the equation have the same root term, \(\displaystyle 3\).

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

\(\displaystyle \small 3^{2x}=9^2\)

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

We can use the power rule to combine exponents.

\(\displaystyle 3^{2x}=3^4\)

Set the exponents equal to each other.

\(\displaystyle 2x=4\)

\(\displaystyle \small x=2\)

Example Question #43 : Exponents

Solve for \(\displaystyle x\):

\(\displaystyle x^3 - 9x =0\)

Possible Answers:

\(\displaystyle x = 0\)

\(\displaystyle x = \{-3,0,3\}\)

\(\displaystyle x = \{-3,3\}\)

\(\displaystyle x = \frac{1}{3}\)

\(\displaystyle x = 3\)

Correct answer:

\(\displaystyle x = \{-3,0,3\}\)

Explanation:

Pull an \(\displaystyle x\) out of the left side of the equation.

\(\displaystyle \rightarrow x(x^2 - 9) =0\)

Use the difference of squares technique to factor the expression in parentheses.

\(\displaystyle \rightarrow x(x+3)(x-3) =0\)

Any number that causes one of the terms \(\displaystyle x\)\(\displaystyle x+3\), or \(\displaystyle x-3\) to equal \(\displaystyle 0\) is a solution to the equation. These are \(\displaystyle 0\)\(\displaystyle -3\), and \(\displaystyle 3\), respectively.

Example Question #1 : Graphing Exponential Functions

Find the \(\displaystyle y\)-intercept(s) of \(\displaystyle y=\frac{x^3+2x+8}{x^2-36}\).

Possible Answers:

\(\displaystyle y=6\)

\(\displaystyle y=-\frac{2}{9}\)

\(\displaystyle y=\frac{2}{9}\)

This function does not cross the \(\displaystyle y\)-axis.

\(\displaystyle y=8\)

Correct answer:

\(\displaystyle y=-\frac{2}{9}\)

Explanation:

To find the \(\displaystyle y\)-intercept, set \(\displaystyle x=0\) in the equation and solve.

\(\displaystyle y=\frac{x^3+2x+8}{x^2-36}\)

\(\displaystyle y=\frac{(0)^3+2(0)+8}{(0)^2-36}\)

\(\displaystyle y=\frac{(0)+(0)+8}{(0)-36}\)

\(\displaystyle y=\frac{8}{-36}\)

\(\displaystyle y=-\frac{2}{9}\)

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