y=x^2+1
d(y)=d(x^2+1)=d(x^2)+d(1)=(x^2)`dx+(1)`dx=2xdx+0dx=2xdx
y=2x+3
d(y)=d(2x+3)=d(2x)+d(3)=(2x)`dx+(3)`dx=2dx+0dx=2dx
