函數y=-x3+48x-3的極大值為______.

函數y=-x3+48x-3的極大值為______.

∵y′=-3x2+48=-3(x+4)(x-4)∴函數y=-x3+48x-3在(-∞,-4)是减函數,在(-4,4)上是增函數,在(4,+∞)是减函數∴函數y=-x3+48x-3在x=4時取得極大值125故答案為:125.