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**Home Assignment 2 / problem4 (20)**

« **on:**January 18, 2019, 11:53:36 PM »

the expression on the right hand contains both x and y,

the characteristic line is 3x-y=c

then, we evaluate du = xydx. in this step, we have to replace y by 3x-c before integrating both sides.

My question is, why we have to do so?

And after integrte both sides, why we have to replace c back by 3x-y?

the characteristic line is 3x-y=c

then, we evaluate du = xydx. in this step, we have to replace y by 3x-c before integrating both sides.

My question is, why we have to do so?

And after integrte both sides, why we have to replace c back by 3x-y?