The maximum value of the function y = 1 + 3x-x & # 179; is

y=1+3x-x³
y'=3-3x²
=-3(x+1)(x-1)=0
x1=-1
x2=1
y''=-6x
y''(-1)=6>0
therefore
X = - 1 is the minimum point
y''(1)=-6
therefore
Take the maximum value at x = 1 = y (1) = 1 + 3-1 = 3

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