16. Consider F(y) = f'¹[(y')² + ry' ]e−²y dx where y(0) = 1, y(1) is free, and r is a constant. Find the extremals. Show there are no extremals if r ≥ r#, and only one extremal if r < r#, where r# is a number that you should find.

5. Let u(r) be a differentiable function with u(1) = 2 and u (1) = 3. Find an equation of the tangent line to the curve y4 +3e"(=)v = [u(x)]² – y² – x %3D at the point (1,0).