Extremal value problems - easy

Problem №1
Find the minimal value of the function $f(x)=3x^3-9x^2+6$ for $x \in [-1;5]$.
Problem №2
Find the maximum value of the function $f(x)=x-5$ if x is a number between -5 and 13.
Problem №3
Find the maximal value for the function $f(x)=4sin(x)$
Problem №4
Find the minimal value for the function $f(x)=|x|-1$.

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