Given the function f (x) = 4x-kx-8, if y = f (x) has a minimum value of - 12 in the interval (∞, 2), then, Don't copy Baidu's answer. I think the wrong one is k = 8 or K = - 8. But when k = 8, the axis of symmetry - B / 2A = - 8 / (2x4) = - 1. When k = - 8, the axis of symmetry - B / 2A = - (- 8) / (2x4) = 1 is different from Baidu's answer

Given the function f (x) = 4x-kx-8, if y = f (x) has a minimum value of - 12 in the interval (∞, 2), then, Don't copy Baidu's answer. I think the wrong one is k = 8 or K = - 8. But when k = 8, the axis of symmetry - B / 2A = - 8 / (2x4) = - 1. When k = - 8, the axis of symmetry - B / 2A = - (- 8) / (2x4) = 1 is different from Baidu's answer

If this interval is on the left side of the axis of symmetry, that is, K ≥ 16, the minimum should be f (2) = 8-2k = - 12, k = 10. If 2 is on the right side of the axis of symmetry, the minimum is f (K / 8) = (k / 16) - (K / 8) - 8 = - K / 16-8 = - 12, k = ± 8

Given the function 4msin χ - Cos2 χ, χ belongs to R, if y max = 3, find the value of real number M

f（x）=4msinx-cos2x=4msinx-（1-2sinxsinx）
=2sinxsinx+4msinx-1
=2（sinx+m）^2-2m^2-1
1. When m = 0, SiNx = 1, f (x) max = 4m + 1 = 3, M = 1 / 2
So the real number m is - 1 / 2 or 1 / 2

Y = 2 + | cosx | find the maximum and minimum value of the function, and find the set of X that makes it obtain the maximum and minimum value

-1