Welcome :: Homework Help and Answers :: Mathskey.com
Welcome to Mathskey.com Question & Answers Community. Ask any math/science homework question and receive answers from other members of the community.

13,459 questions

17,854 answers

1,446 comments

811,087 users

First make a substitution and then use integration by parts to evaluate the integral.?

0 votes
First make a substitution and then use integration by parts to evaluate the integral.
∫ t^15 e^-t^8 dt
asked Apr 24, 2013 in CALCULUS by Jose Rodriguez Rookie

2 Answers

0 votes

integral t to the power of 15 open parentheses e close parentheses to the power of minus t to the power of 8 end exponent d t equal integral t to the power of 8 cross times t to the power of 7 open parentheses e close parentheses to the power of minus t to the power of 8 end exponent d t   

space space space space space space space space space space space space space space space space space space space space equal integral x cross times t to the power of 7 d t open parentheses e close parentheses to the power of minus x end exponent      (L e t space t to the power of 8 equal x space t h e n space 8 t to the power of 7 d t equal d x)

space space space space space space space space space space space space space space space space space space space space equal integral x cross times 1 over 8 d x open parentheses e close parentheses to the power of minus x end exponent   (Substitute t to the power of 7 d t equal 1 over 8 d x)

space space space space space space space space space space space space space space space space space space space space equal 1 over 8 integral x cross times open parentheses e close parentheses to the power of minus x end exponent d x    

space space space space space space space space space space space space space space space space space space space space equal 1 over 8 open square brackets x integral open parentheses e close parentheses to the power of minus x end exponent d x minus integral open parentheses 1 x to the power of 0 integral open parentheses e close parentheses to the power of minus x end exponent d x close parentheses d x close square brackets

                                                     (integral f open parentheses x close parentheses g open parentheses x close parentheses d x equal f open parentheses x close parentheses integral g open parentheses x close parentheses d x minus integral open parentheses d open parentheses f open parentheses x close parentheses close parentheses integral g open parentheses x close parentheses d x close parentheses d x right parenthesis

space space space space space space space space space space space space space space space space space space space space equal 1 over 8 open square brackets x open parentheses minus e to the power of minus x end exponent close parentheses minus integral minus e to the power of minus x end exponent d x close square brackets

space space space space space space space space space space space space space space space space space space space space equal 1 over 8 open square brackets x open parentheses minus e to the power of minus x end exponent close parentheses minus e to the power of minus x end exponent close square brackets

space space space space space space space space space space space space space space space space space space space space equal fraction numerator minus e to the power of minus x end exponent over denominator 8 end fraction open square brackets x plus 1 close square brackets

space space space space space space space space space space space space space space space space space space space space equal fraction numerator minus e to the power of minus t to the power of 8 end exponent over denominator 8 end fraction open square brackets t to the power of 8 plus 1 close square brackets      (Substitute x equal t to the power of 8)

 

 


 

answered Apr 24, 2013 by diane Scholar
0 votes

image

Substitution method

image

image

image

image

Now the integral becomes image

image

image

By parts of integration formulaimage

image

image

image

image

image

image

image

image

image

image

Again substitute image

image

image

answered Jul 9, 2014 by david Expert

Related questions

...