Find x(t) that extremizes the following functional

a) J[x] = ∫₁² x²/4t dt with x (1) = 5 x(2) = 11
b) J[x] = ∫0 7 (1+x2)1/2 / x dt with x(0) = 4, x(7) = 3 and x > 0 in the integration range.