Let the quadratic function f (x) = x ^ 2 + BX + C satisfy f (1) = - 4, f (2) = - 3,5 * f (4), and find the minimum value of this function

Let the quadratic function f (x) = x ^ 2 + BX + C satisfy f (1) = - 4, f (2) = - 3,5 * f (4), and find the minimum value of this function


Directly substitute f (1), f (2), f (4) to get B + C = - 5, 11b + 4C = - 34, so B = - 2, C = - 3, f (x) = x ^ 2-2x-3 = (x-1) ^ 2-4, so the minimum value is - 4