restart;
f:=-4*x^2+8*x;
g:=x;


plot([f,g],x=0..2);

solve(f=g,x);

Ax:=int(Pi*(f^2-g^2),x=0..7/4);

evalf(Ax);

Ay:=int(2*Pi*x*(f-g),x=0..7/4);

evalf(Ay);