Starting from the initial trial solution (x1, x2) = (0, 0), apply one iteration of the gradient

Question:

Starting from the initial trial solution (x1, x2) = (0, 0), apply one iteration of the gradient search procedure to the following problem by hand:
Maximize f(x) = 4x1 + 2x2 + x21 - x41 - 2x1x2 - x22.
To complete this iteration, approximately solve for t* by manually applying two iterations of the bisection method t = 0, t-bar = 1.