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Mathematics 7 Online
OpenStudy (anonymous):

\int\limits_6^10( dx/x+2)

OpenStudy (anonymous):

ganeshie8 (ganeshie8):

hint : \(\large \mathbb{\frac{d}{dx}(\ln (x+2)) = \frac{1}{x+2}}\)

OpenStudy (anonymous):

Ok thank you :)

ganeshie8 (ganeshie8):

np :) so u can evaluate the integral now ha ?

OpenStudy (anonymous):

i tried but i don't know the steps lol

ganeshie8 (ganeshie8):

\(\large \mathbb{\int_6^{10} \frac{1}{x+2} dx}\) \(\large \mathbb{ \ln(x+2) \Big|_2^4}\)

ganeshie8 (ganeshie8):

fine so far ?

OpenStudy (anonymous):

ok but there is not x it's x+2 and the formula is integral 1/x dx? so there's x+2..

OpenStudy (anonymous):

i mean x+2?

OpenStudy (anonymous):

integral 1/x+2 dx =ln (x+2?

OpenStudy (anonymous):

@ganeshie8

ganeshie8 (ganeshie8):

very good question :)

OpenStudy (anonymous):

:) i know i am not good at math.little slow actually

ganeshie8 (ganeshie8):

\(\large \mathbb{\int \frac{1}{x+2} dx = \ln(x+2) + c}\)

ganeshie8 (ganeshie8):

if you differentiate the right side, wat wud u get ?

ganeshie8 (ganeshie8):

nope, u r doing great lol :)

OpenStudy (anonymous):

i will get 0? like ln (x+2)/0?

OpenStudy (anonymous):

d/dx(2)=0

ganeshie8 (ganeshie8):

noo u need to use chain rule

ganeshie8 (ganeshie8):

\(\large \mathbb{\frac{d}{dx} \ln (x+2) = \frac{1}{x+2} * \frac{d}{dx}(x+2)}\) \(\large \mathbb{~~~~~~~~~~~~~= \frac{1}{x+2} * (1+0)}\) \(\large \mathbb{~~~~~~~~~~~~~= \frac{1}{x+2} }\)

ganeshie8 (ganeshie8):

so we say, \(\large \mathbb{\int \frac{1}{x+2} = \ln (x+2)}\) okay ?

OpenStudy (anonymous):

oh i got it lol thank u :)

ganeshie8 (ganeshie8):

good, so the integral becomes : \(\large \mathbb{\int_6^{10} \frac{1}{x+2} dx}\) \(\large \mathbb{ \ln(x+2) \Big|_2^4}\)

ganeshie8 (ganeshie8):

if u evaluate the bounds u wud get : \(\large \mathbb{ \ln(x+2) \Big|_2^4}\) \(\large \mathbb{ \ln(4+2) - \ln(2+2) }\) \(\large \mathbb{ \ln(6) - \ln(4) }\) \(\large \mathbb{ \ln(\frac{6}{4}) }\) \(\large \mathbb{ \ln(\frac{3}{2}) }\)

ganeshie8 (ganeshie8):

see if that makes more or less sense :)

OpenStudy (anonymous):

yeah it does lol :) thank u :)

ganeshie8 (ganeshie8):

good to hear.... u wlc :)

OpenStudy (anonymous):

:)

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