$1\mathrm{.}7\mathrm{.}1$ For the systems described $by$ the following equations, with the input $x(t)$ and output $y(t),$ determine which $of$ the

systems are linear and which are nonlinear.

$a.\frac{dy}{dt}+2y(t)=x^2(t)$

$b.\frac{dy}{dt}+3ty(t)=t^{2}x(t)$

$c.3y(t)+2=x(t)$

$d.\frac{dy}{dt}+y^2(t)=x(t)$

$e.(\frac{dy}{dt}{)}^2+2y(t)=x(t)$

$f.\frac{dy}{dt}+(sint)y(t)=\frac{dx}{dt}+2x(t)$

$g.\frac{dy}{dt}+2y(t)=x(t)\frac{dx}{dt}$

$h.y(t)={\displaystyle \underset{-}{\overset{t}{}}}x()d$