[tex]a=\frac{1}{4}\;\;si\;\;b=\frac{9}{4}\\
a)...\;\;m_a=\frac{a+b}{2}=\frac{1/4+9/4}{2}=10/4\;:\;2=10/4\cdot1/2=10/8=5/4;\\
b)...\;\;m_g=\sqrt{1/4\cdot9/4}=3/4;\\
c)...\;\;x=pretul\;initial\\
\rightarrow\;x\cdot\frac{100-10}{100}=90(lei)\;\Rightarrow\;x=\frac{90\cdot100}{90}=100(lei)
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