1.

Solve the differential equation: `(1+x^2) dy/dx + y = tan^-1 x`

Answer» `(dy)/(dx)+y/(1+x^2)=tan^(-1)x/(1+x^2)`
P=`1/(1+x^2)` Q=`(tan^(-1)x)/(1+x^2)`
`y*IF=int(IF)*Q dx`
`y*e^(tan^(-1)x)=int(e^(tan^(-1)x))/(1+x^2) dx`
let`tan^(-1)x=t`
`y*e^t=(t-1)e^t+c`
`y=(tan^(-1)x-1)+ce^(-tan^(-1)x)`.


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