Hello, help me please with equation d.In the equation d) The IVT applies, then I should find all values of c, but the discriminant there is

Exercises - Intermediate Value Theorem 1. Decide whether or not the Intermediate Value Theorem can be applied to the given function, value, and interval. Justify your decision carefully. When this theorem applies, state carefully what it concludes. Finally, find all values c in the given interval, such that f (c) = k. a. f (x) = x' - 2x + 1; k =4, [-3, 2] b. f (x) = 4x4 -9; k = 0, [1, 20 c. f (x) = -x2 + 3x; k = 0, [-1, 2] d. f (x) = x' tx+1; k =7, [-2,3]