f(x)=x³-3x [0;3]
f'(x)=3x²-3=0
3x²-3=0 |÷3
x²=1
x₁=1
x₂=-1 ∉ [0;3]
f(0)=0³-3*0=0
f(1)=1³-3*1=1-3=-2=fнаим.
f(3)=3³*3*3=27-9=18.
