Correct Answer - a
The Given differential equation is
` (dy)/(dx) + P (x)* y = Q (x) * y^(n)`
` rArr 1/(y^(n)) * (dy)/(dx) + y^(-n+1) P y = Q (x)* y^(n)`
Put ` 1/(y^(n-1))= v `
` rArr (-n +1) y^(-n)(dy)/(dx) =(dv)/(dx)`
` :. 1/(-n+1) * (dv)/(dx) +P (x) * v = Q (x)`
` rArr (dv)/(dx) +(1-n) P (x) * v = (1-n) Q (x)`
which is linear differential equation .
Hence , required substitiution is ` v = 1/(y^(n-1))`
