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Mathematics 21 Online
OpenStudy (anonymous):

integral help

OpenStudy (anonymous):

hartnn (hartnn):

Partial fractions, know what that is ?

OpenStudy (anonymous):

for the first question? I can use partial fractions straight away?

hartnn (hartnn):

infact partial fractions may not be even required. just a u substitution can solve it

hartnn (hartnn):

the denominator is a perfect square, isn't it ? of what ?

OpenStudy (anonymous):

(x+1)^2

hartnn (hartnn):

yes, so you could just do u = x+1 x= .. du = ...?

OpenStudy (anonymous):

du = dx?

hartnn (hartnn):

correct and x = u-1 now plug these into your original integral to make a new integral

OpenStudy (anonymous):

wait sorry, why does x = u-1, where does the u-1 come from?

OpenStudy (anonymous):

i would help but im clueless

hartnn (hartnn):

u = x+1 x= .... ?

hartnn (hartnn):

because we will need 'x' in terms of 'u' for the numerator

OpenStudy (anonymous):

ok

hartnn (hartnn):

so whats your new integral ?

OpenStudy (anonymous):

integral of 7(u-1)+13 / u^2 ?

hartnn (hartnn):

correct is that easy for you to solve ?

OpenStudy (anonymous):

sorry, I'm not good at any of differentiation or integral problems. Would you try split it in two terms of something?

hartnn (hartnn):

thats correct (7u+6)/u^2 = 7/u + 6/u^2 then use x^n formula for 2nd term and 1/x formula for the first term, you have the formula list ?

OpenStudy (anonymous):

can you just find the integral of 7u^-1 and 6u^-2?

hartnn (hartnn):

i can yes i'll give you the formula so that you can too \(\int (1/x)dx = \ln |x|+c \\ \int x^n dx = \dfrac{x^{n+1}}{n+1}+c\)

hartnn (hartnn):

for 2nd term, since we have u^-2 plug in n=-2

OpenStudy (anonymous):

ok, so I'm not sure if i'm doing it correctly at all but would you get log|u| - 1/u + 2C?

hartnn (hartnn):

what about constants 7 and 6?

OpenStudy (anonymous):

and then you substitute your u=x+1 if that's correct I believe

OpenStudy (anonymous):

the 7 will remain in front of log|u|? and 6 will remain in front of -1/u ?

hartnn (hartnn):

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