What is the simplest way to approach this integral problem? To me, this problem seemed to necessitate some kind of gimmick.

85 Views Asked by At

enter image description here

How can I tackle this problem with as few abstract ideas as possible when attempting to 'purely' integrate from left to right? I've tried a few different versions of this term, but I'm not sure how to get into an answer. Is there another way to approach this?

1

There are 1 best solutions below

5
On BEST ANSWER

Just a bit of manipulation and you have the answer. Split the integral this way. $\int(t+1-\frac{1}{t}).e^{t+ \frac{1}{t}}+ \int(1-\frac{1}{t^2}).e^{t+ \frac{1}{t}}$ Now right side easily evaluates to $e^{t+ \frac{1}{t}}$. For the left the side multiply and divide it by $t$ and write it as $t(\frac{1}{t} + 1- \frac{1}{t^2})$ . Then the left integral becoems $\int e^{t+ \frac{1}{t}}dt + \int t(1-\frac {1}{t^2})e^{t+ \frac{1}{t}}dt$. Now here in the right side integral take $t$ as the 1st and the rest as the 2nd function(and using by parts integration).So the right integral on integrating becomes $t.e^{t+ \frac{1}{t}}$$- \int e^{t+ \frac{1}{t}}.dt$ which cancels the left most term of the integral hence we finally obtain the integral as $(t+1).e^{t+ \frac{1}{t}} + C$