Solution
Classic version
1. Marking characteristic points and reactions at supports

3. Decomposition of internal force equations in individual variability intervals:
a)Interval AB 


Extremum
\begin{aligned} \\ &\frac{10}{x}=\frac{30}{4-x} \ \Rightarrow \ x=1\\ &M_{max}=10\cdot 1 – 10\cdot(\frac{1}{2})^{2}=5\\ \\ \end{aligned}b) Interval BC 

c) Interval DC 

4. Final graphs

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