f(x)=3(x+x-1)
keep 3 alone for the calculation and consider it at last for final answer
⟹f'(x)=1–x-2
Critical point(s):
f′(x)=0
1−x-2=0
⟹x=±1
f′′(x)=2x-3
f′′(−1)=−2, f′′(1)=2
Maximum value of f(x):f(−1)=−2 * 3 = -6
Minimum value of f(x):f(1)=2 * 3 = 6
