Answer
(a) it is linear with $P=x^2$ and $Q=1$.
(b) it is non linear.
(c) it is linear with $P=x^{-5}$ and $Q=x^{-5} e^x$.
(d) it is non linear.
Work Step by Step
Since the general form of the first order linear equation is
$$y'+P(x)y=Q(x)$$
Then we have
(a) the equation is linear with $P=x^2$ and $Q=1$.
(b) the equation is non linear.
(c) the equation is linear with $P=x^{-5}$ and $Q=x^{-5} e^x$.
(d) the equation is non linear.
