In Problems 1-8, identify (do not solve) the equation as homogeneous, Bernoulli, linear coefficients, or of the form \text { 1. } 2 t x d x+\left(t^{2}-x^{2}\right) d t=0 \text

{ 3. } d y / d x+y / x=x^{3} y^{2} \text { 5. } \theta d y-y d \theta=\sqrt{\theta y} d \theta \text { 7. } \cos (x+y) d y=\sin (x+y) d x