Calculus 2 : Finding Integrals

Study concepts, example questions & explanations for Calculus 2

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Example Questions

Example Question #2492 : Calculus Ii

Evaluate.

\displaystyle \int 12x-9 dx

Possible Answers:

\displaystyle F(x) = 6x^2-9x + C

\displaystyle F(x) = 3x-5 + C

\displaystyle F(x) = 6x-9 + C

\displaystyle F(x) = 12x^2-9 + C

Answer not listed.

Correct answer:

\displaystyle F(x) = 6x^2-9x + C

Explanation:

\displaystyle \int f(x) dx

In order to evaluate this integral, first find the antiderivative of \displaystyle f(x).

If \displaystyle f(x) = a then \displaystyle F(x) = ax + C

If \displaystyle f(x) = x a then \displaystyle F(x) = \frac{x^{a+1}}{a+1} + C

If \displaystyle f(x) = \frac{1}{x} then \displaystyle F(x) = ln(x) + C

If \displaystyle f(x) = e ^x then \displaystyle F(x) = e^x + C

If \displaystyle f(x) = \cos(x) then \displaystyle F(x) = \sin(x) + C

If \displaystyle f(x) = \sin(x) then \displaystyle F(x) = - \cos(x) + C

If \displaystyle f(x) = \sec^2 (x) then \displaystyle F(x) = \tan(x) + C

 

In this case, \displaystyle f(x) = 12x-9.

The antiderivative is  \displaystyle F(x) = 6x^2-9x + C.

Example Question #121 : Indefinite Integrals

Integrate:

\displaystyle \int (4x+\frac{1}{16+x^2})dx

Possible Answers:

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

\displaystyle 2x^2+\frac{\arctan(\frac{x}{4})}{4}

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

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

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

Correct answer:

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

Explanation:

The integral is equal to

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

 

and was found using the following rules:

\displaystyle \int x^ndx=\frac{x^{n+1}}{n+1}+C\displaystyle \int \frac{dx}{x^2+a^2}=\frac{1}{a}\arctan(\frac{x}{a})+C

Example Question #122 : Indefinite Integrals

\displaystyle \int x\sqrt{x^2-1}dx

Possible Answers:

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

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

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

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

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

Correct answer:

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

Explanation:

To integrate this expression, use u substitution:

\displaystyle u=x^2-1; du=2xdx; \frac{1}{2}du=xdx

Now, substitute in everything and rewrite the expression: 

\displaystyle \frac{1}{2}\int u^{\frac{1}{2}}du

Integrate and remember to raise the exponent by 1 and then put that result on the denominator: 

\displaystyle (\frac{1}{2})(\frac{u^{\frac{3}{2}}}{\frac{3}{2}})

Simplify and sub back in your initial expression:

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

Remember to add C because it is an indefinite integral:
\displaystyle \frac{(x^2-1)^{\frac{3}{2}}}{3}+C.

 

 

Example Question #751 : Integrals

\displaystyle \int 2x\sqrt{x^2-4}dx

Possible Answers:

    \displaystyle \frac{2}{3}(x^2-4)^{\frac{3}{2}}+C

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

\displaystyle \frac{2}{3}(x^2+4)^{\frac{3}{2}}+C

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

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

Correct answer:

    \displaystyle \frac{2}{3}(x^2-4)^{\frac{3}{2}}+C

Explanation:

To integrate this expression, use u substitution:

\displaystyle u=x^2-4; du=2xdx

Now, substitute everything in and rewrite the expression:

\displaystyle \frac{u^{\frac{3}{2}}}{\frac{3}{2}}

Now, simplify and sub back in your initial expression:

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

Don't forget to add a C because it is an indefinite integral:

\displaystyle \frac{2}{3}(x^2-4)^{\frac{3}{2}}+C.

Example Question #124 : Indefinite Integrals

\displaystyle \int \frac{4x^2-16x+12}{4}dx

Possible Answers:

\displaystyle \frac{x^3}{3}-2x^2+3x+C

\displaystyle \frac{x^3}{3}-2x+3+C

\displaystyle \frac{x}{3}-2x^2+3x+C

\displaystyle \frac{x^3}{3}-2x^2+3x

\displaystyle \frac{x^3}{3}-2x^2+3+C

Correct answer:

\displaystyle \frac{x^3}{3}-2x^2+3x+C

Explanation:

First, chop up this fraction into three separate terms so you can more easily integrate:

\displaystyle \int x^2-4x+3dx

Now, integrate. Remember to add one to the exponent and also put that result on the denominator:

\displaystyle \frac{x^3}{3}-\frac{4x^2}{2}+3x

Simplify and add a C because it is an indefinite integral:

\displaystyle \frac{x^3}{3}-2x^2+3x+C.

Example Question #751 : Integrals

\displaystyle \int 2x^2+x-1dx

Possible Answers:

\displaystyle \frac{x^3}{3}+\frac{x^2}{2}-x+C

\displaystyle \frac{2x^3}{3}+\frac{x^2}{2}-2x+C

\displaystyle \frac{2x^3}{3}+\frac{x^2}{2}-x+C

\displaystyle \frac{2x^3}{3}+\frac{3x^2}{2}-x+C

\displaystyle \frac{2x^3}{3}+\frac{x^2}{2}-x

Correct answer:

\displaystyle \frac{2x^3}{3}+\frac{x^2}{2}-x+C

Explanation:

To integrate, remember to raise the exponent by 1 and then put that result on the denominator:

\displaystyle \frac{2x^3}{3}+\frac{x^2}{2}-x

Remember to add a C because it is an indefinite integral:

\displaystyle \frac{2x^3}{3}+\frac{x^2}{2}-x+C

Example Question #756 : Integrals

Evaluate.

\displaystyle \int 13i \ dx

Possible Answers:

\displaystyle F(x) = 13ix^2 +C

\displaystyle F(x) = 13ix +C

\displaystyle F(x) = 13i +C

\displaystyle F(x) = ix +C

Answer not listed

Correct answer:

\displaystyle F(x) = 13ix +C

Explanation:

\displaystyle \int f(x) dx

In order to evaluate this integral, first find the antiderivative of \displaystyle f(x).

If \displaystyle f(x) = a then \displaystyle F(x) = ax + C

If \displaystyle f(x) = x a then \displaystyle F(x) = \frac{x^{a+1}}{a+1} + C

If \displaystyle f(x) = \frac{1}{x} then \displaystyle F(x) = ln(x) + C

If \displaystyle f(x) = e ^x then \displaystyle F(x) = e^x + C

If \displaystyle f(x) = \cos(x) then \displaystyle F(x) = \sin(x) + C

If \displaystyle f(x) = \sin(x) then \displaystyle F(x) = - \cos(x) + C

If \displaystyle f(x) = \sec^2 (x) then \displaystyle F(x) = \tan(x) + C

 

In this case, \displaystyle f(x) = 13i.

The antiderivative is  \displaystyle F(x) = 13ix +C.

Example Question #757 : Integrals

Evaluate.

\displaystyle \int \frac{x}{3-x} \ dx

Possible Answers:

\displaystyle F(x) = - \ln(x) - x+C

\displaystyle F(x) = -3 \ln(3-x)+C

Answer not listed

\displaystyle F(x) = \ln(3-x)+C

\displaystyle F(x) = \ln(3-x) + 3x+C

Correct answer:

Answer not listed

Explanation:

\displaystyle \int f(x) dx

In order to evaluate this integral, first find the antiderivative of \displaystyle f(x).

If \displaystyle f(x) = a then \displaystyle F(x) = ax + C

If \displaystyle f(x) = x a then \displaystyle F(x) = \frac{x^{a+1}}{a+1} + C

If \displaystyle f(x) = \frac{1}{x} then \displaystyle F(x) = ln(x) + C

If \displaystyle f(x) = e ^x then \displaystyle F(x) = e^x + C

If \displaystyle f(x) = \cos(x) then \displaystyle F(x) = \sin(x) + C

If \displaystyle f(x) = \sin(x) then \displaystyle F(x) = - \cos(x) + C

If \displaystyle f(x) = \sec^2 (x) then \displaystyle F(x) = \tan(x) + C

 

In this case, \displaystyle f(x) = \frac{x}{3-x}.

The antiderivative is  \displaystyle F(x) = -3 \ln(3-x) - x+C.

Example Question #752 : Integrals

Evaluate.

\displaystyle \int e^{2x-5} \ dx

Possible Answers:

Answer not listed.

\displaystyle F(x) = e^{2x-5} +C

\displaystyle F(x) = 2e^{2x-5} +C

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

\displaystyle F(x) = \frac{e^{2x-5} }{2} +C

Correct answer:

\displaystyle F(x) = \frac{e^{2x-5} }{2} +C

Explanation:

\displaystyle \int f(x) dx

In order to evaluate this integral, first find the antiderivative of \displaystyle f(x).

If \displaystyle f(x) = a then \displaystyle F(x) = ax + C

If \displaystyle f(x) = x a then \displaystyle F(x) = \frac{x^{a+1}}{a+1} + C

If \displaystyle f(x) = \frac{1}{x} then \displaystyle F(x) = ln(x) + C

If \displaystyle f(x) = e ^x then \displaystyle F(x) = e^x + C

If \displaystyle f(x) = \cos(x) then \displaystyle F(x) = \sin(x) + C

If \displaystyle f(x) = \sin(x) then \displaystyle F(x) = - \cos(x) + C

If \displaystyle f(x) = \sec^2 (x) then \displaystyle F(x) = \tan(x) + C

 

In this case, \displaystyle f(x) = e^{2x-5}.

The antiderivative is  \displaystyle F(x) = \frac{e^{2x-5} }{2} +C.

Example Question #753 : Integrals

Evaluate.

\displaystyle \int \sin (5x-3) \ dx

Possible Answers:

\displaystyle F(x) = -\frac{ \cos(5x-3) }{5x-3} +C

\displaystyle F(x) = \frac{ \cos(5x-3) }{x} +C

\displaystyle F(x) = -\frac{ \cos(5x-3) }{5} +C

\displaystyle F(x) = -\frac{ \sin(5x) }{5} +C

Answer not listed.

Correct answer:

\displaystyle F(x) = -\frac{ \cos(5x-3) }{5} +C

Explanation:

\displaystyle \int f(x) dx

In order to evaluate this integral, first find the antiderivative of \displaystyle f(x).

If \displaystyle f(x) = a then \displaystyle F(x) = ax + C

If \displaystyle f(x) = x a then \displaystyle F(x) = \frac{x^{a+1}}{a+1} + C

If \displaystyle f(x) = \frac{1}{x} then \displaystyle F(x) = ln(x) + C

If \displaystyle f(x) = e ^x then \displaystyle F(x) = e^x + C

If \displaystyle f(x) = \cos(x) then \displaystyle F(x) = \sin(x) + C

If \displaystyle f(x) = \sin(x) then \displaystyle F(x) = - \cos(x) + C

If \displaystyle f(x) = \sec^2 (x) then \displaystyle F(x) = \tan(x) + C

 

In this case, \displaystyle f(x) = \sin (5x-3).

The antiderivative is  \displaystyle F(x) = -\frac{ \cos(5x-3) }{5} +C.

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