Calculus 1 : Writing Equations

Study concepts, example questions & explanations for Calculus 1

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Example Questions

Example Question #91 : Equations

Evaluate the following indefinite integral:

\(\displaystyle \int (sin(x))^{3}cos(x)dx\)

Possible Answers:

\(\displaystyle \frac{1}{3}(sin(x))^{4}+C\)

\(\displaystyle \frac{1}{4}(sin(x))^{3}+C\)

\(\displaystyle 4(sin(x))^{4}+C\)

\(\displaystyle \frac{1}{4}(sin(x))^{4}+C\)

Correct answer:

\(\displaystyle \frac{1}{4}(sin(x))^{4}+C\)

Explanation:

To solve this problem we have to use a u substitution. A "u-sub" is done by using the following steps:

1. Set u equal to the x equation in parentheses, take the derivative, and solve:

\(\displaystyle u=sin(x)\)

\(\displaystyle du=cos(x)dx\)

2. Replace x values with u values and integrate accordingly:

\(\displaystyle \int u^{3}du=\frac{u^{3+1}}{3+1}=\frac{u^{4}}{4}\)

3. Put the original x equation back in for u and add "C":

\(\displaystyle \frac{u^{4}}{4}=\frac{1}{4}(sin(x))^{4}+C\)

 

Example Question #92 : Equations

Evaluate the following indefinite integral:

\(\displaystyle \int (sec(2x))^{2}dx\)

Possible Answers:

\(\displaystyle tan(2x)+C\)

\(\displaystyle 2tan(2x)+C\)

\(\displaystyle \frac{1}{2}tan(2x)+C\)

\(\displaystyle \frac{1}{4}tan(2x)+C\)

Correct answer:

\(\displaystyle \frac{1}{2}tan(2x)+C\)

Explanation:

To solve this problem we have to use a u substitution. We also need to remember our properties of trig functions. A "u-sub" is done by using the following steps:

1. Set u equal to the x equation in parentheses, take the derivative, and solve:

\(\displaystyle u=2x\)

\(\displaystyle du=2dx\)

\(\displaystyle dx=\frac{1}{2}du\)

2. Replace x values with u values and integrate accordingly:

\(\displaystyle \int (sec(u))^{2}*\frac{1}{2}du=\frac{1}{2}tan(u)\)

3. Put the original x equation back in for u and add "C":

\(\displaystyle \frac{1}{2}tan(u)=\frac{1}{2}tan(2x)+C\)

Example Question #91 : Writing Equations

Evaluate the following indefinite integral:

\(\displaystyle \int e^{x}dx\)

Possible Answers:

\(\displaystyle e^{x}+C\)

\(\displaystyle \frac{1}{3}e^{x}+C\)

\(\displaystyle e^{2x}+C\)

\(\displaystyle 2e^{x}+C\)

Correct answer:

\(\displaystyle e^{x}+C\)

Explanation:

To solve this problem, all we have to remember is that the integral of e doesn't change. That gives us the following:

\(\displaystyle \int e^{x}dx=e^{x}+C\)

Example Question #94 : Equations

Evaluate the following indefinite integral:

\(\displaystyle \int e^{2x}dx\)

Possible Answers:

\(\displaystyle 2e^{2x}+C\)

\(\displaystyle \frac{1}{2}e^{2x}+C\)

\(\displaystyle e^{2x}+C\)

\(\displaystyle \frac{1}{4}e^{2x}+C\)

Correct answer:

\(\displaystyle \frac{1}{2}e^{2x}+C\)

Explanation:

To solve this problem we have to use a u substitution. A "u-sub" is done by using the following steps:

1. Set u equal to the x equation in parentheses, take the derivative, and solve:

\(\displaystyle u=2x\)

\(\displaystyle du=2dx\)

\(\displaystyle dx=\frac{1}{2}du\)

2. Replace x values with u values and integrate accordingly:

\(\displaystyle \int e^{u}*\frac{1}{2}du=\frac{1}{2}e^{u}\)

3. Put the original x equation back in for u and add "C":

\(\displaystyle \frac{1}{2}e^{u}=\frac{1}{2}e^{2x}+C\)

Example Question #95 : Equations

Evaluate the following indefinite integral:

\(\displaystyle \int 3e^{6x}dx\)

Possible Answers:

\(\displaystyle \frac{1}{2}e^{6x}+C\)

\(\displaystyle \frac{1}{6}e^{6x}+C\)

\(\displaystyle \frac{1}{3}e^{6x}+C\)

\(\displaystyle e^{6x}+C\)

Correct answer:

\(\displaystyle \frac{1}{2}e^{6x}+C\)

Explanation:

To solve this problem we have to use a u substitution. A "u-sub" is done by using the following steps:

1. Set u equal to the x equation in parentheses, take the derivative, and solve:

\(\displaystyle u=6x\)

\(\displaystyle du=6dx\)

\(\displaystyle dx=\frac{1}{6}du\)

2. Replace x values with u values and integrate accordingly:

\(\displaystyle \int 3e^{u}*\frac{1}{6}du= \int \frac{1}{2}e^{u}du=\frac{1}{2}e^{u}\)

3. Put the original x equation back in for u and add "C":

\(\displaystyle \frac{1}{2}e^{u}=\frac{1}{2}e^{6x}+C\)

Example Question #96 : Equations

Evaluate the following indefinite integral:

\(\displaystyle \int (x + sin(x))dx\)

Possible Answers:

\(\displaystyle \frac{1}{2}x^{2}+cos(x)+C\)

\(\displaystyle \frac{1}{2}x^{2}-cos(x)+C\)

\(\displaystyle x^{2}-cos(x)+C\)

\(\displaystyle 2x^{2}+cos(x)+C\)

Correct answer:

\(\displaystyle \frac{1}{2}x^{2}-cos(x)+C\)

Explanation:

To solve this integral, we use the power rule for the first term:

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

And use the laws of trig functions for the second term:

\(\displaystyle \int sin(x)dx= -cos(x)\)

We can combine these terms and add our "C" to get the final answer:

\(\displaystyle \frac{1}{2}x^{2}-cos(x)+C\)

Example Question #97 : Equations

Evaluate the following indefinite integral:

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

Possible Answers:

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

\(\displaystyle \frac{1}{9}(3x+2)^{3}+C\)

\(\displaystyle \frac{1}{3}(3x+2)^{3}+C\)

\(\displaystyle 9(3x+2)^{3}+C\)

Correct answer:

\(\displaystyle \frac{1}{9}(3x+2)^{3}+C\)

Explanation:

To solve this problem we have to use a u substitution. A "u-sub" is done by using the following steps:

1. Set u equal to the x equation in parentheses, take the derivative, and solve:

\(\displaystyle u=3x+2\)

\(\displaystyle du=3dx\)

\(\displaystyle dx=\frac{1}{3}du\)

2. Replace x values with u values and integrate accordingly:

\(\displaystyle \int u^{2}*\frac{1}{3}du=\frac{u^{2+1}}{3*(2+1)}=\frac{u^{3}}{9}\)

3. Put the original x equation back in for u and add "C":

\(\displaystyle \frac{u^{3}}{9}=\frac{1}{9}(3x+2)+C\)

Example Question #98 : Equations

Evaluate the following indefinite integral:

\(\displaystyle \int (2x+6)^{3}dx\)

Possible Answers:

\(\displaystyle \frac{1}{4}(2x+6)^{4}+C\)

\(\displaystyle \frac{1}{8}(2x+6)^{4}+C\)

\(\displaystyle \frac{1}{2}(2x+6)^{4}+C\)

\(\displaystyle 8(2x+6)^{4}+C\)

Correct answer:

\(\displaystyle \frac{1}{8}(2x+6)^{4}+C\)

Explanation:

To solve this problem we have to use a u substitution. A "u-sub" is done by using the following steps:

1. Set u equal to the x equation in parentheses, take the derivative, and solve:

\(\displaystyle u=2x+6\)

\(\displaystyle du=2dx\)

\(\displaystyle dx=\frac{1}{2}du\)

2. Replace x values with u values and integrate accordingly:

\(\displaystyle \int u^{3}*\frac{1}{2}du=\frac{u^{3+1}}{2*(3+1)}=\frac{u^{4}}{8}\)

3. Put the original x equation back in for u and add "C":

\(\displaystyle \frac{u^{4}}{8}=\frac{1}{8}(2x+6)^{4}+C\)

Example Question #99 : Equations

Evaluate the following indefinite integral:

\(\displaystyle \int sin(3x)dx\)

Possible Answers:

\(\displaystyle -3cos(3x)+C\)

\(\displaystyle 3cos(3x)+C\)

\(\displaystyle -\frac{1}{3}cos(3x)+C\)

\(\displaystyle \frac{1}{3}cos(3x)+C\)

Correct answer:

\(\displaystyle -\frac{1}{3}cos(3x)+C\)

Explanation:

To solve this problem we have to use a u substitution. A "u-sub" is done by using the following steps:

1. Set u equal to the x equation in parentheses, take the derivative, and solve:

\(\displaystyle u=3x\)

\(\displaystyle du=3dx\)

\(\displaystyle dx=\frac{1}{3}du\)

2. Replace x values with u values and integrate accordingly:

\(\displaystyle \int sin(u)*\frac{1}{3}du=-\frac{1}{3}cos(u)\)

3. Put the original x equation back in for u and add "C":

\(\displaystyle -\frac{1}{3}cos(u)=-\frac{1}{3}cos(3x)+C\)

Example Question #100 : Equations

Evaluate the following indefinite integral:

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

Possible Answers:

\(\displaystyle \frac{1}{3}x^{3}+\frac{1}{2}x^{2}+C\)

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

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

\(\displaystyle \frac{1}{3}x^{3}+\frac{3}{2}x^{2}+C\)

Correct answer:

\(\displaystyle \frac{1}{3}x^{3}+\frac{3}{2}x^{2}+C\)

Explanation:

To solve this integral, use the power rule. Applying it to this problem gives us the following for the first term:

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

And the following for the second term:

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

We can combine these terms and add our "C" to get the final answer:

\(\displaystyle \frac{1}{3}x^{3}+\frac{3}{2}x^{2}+C\)

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