(%i1) x=5;

(%i2) y=%o1+5^2;

(%i14) f1=x^4+5*x^2;

(%i16) solve([%o14],[x]);

(%i17) f(x,y):= sin(x) + cos(y);
plot3d(f(x,y), [x,-7,9], [y,-4,8]);