F(x) = (x + 1)(x - 3)(x - 4)

f(x)  x^3 - 2x^2 + 5x + 12

Step-by-step explanation:

Next time please share the goal.  I'm guessing your intent was to multiply out the given function.

f(x) = (x^2 + x - 3x - 3)(x - 4), or

      = (x^2 - 2x - 3)(x - 4)

Now apply the distributive property of multiplication:

f(x) = x^3 - 4x^2 - 2x^2 + 8x - 3x + 12, or

      = x^3 - x^2(4 - 2) + x(5) + 12, or

f(x)  x^3 - 2x^2 + 5x + 12

the first question mark is 6 and the second question mark is 26 (the square root)

step-by-step explanation: