Zadanie 1
P=\frac{a+b}{2}*c
\frac{a+b}{2}*c=P |*2
(a+b)*c=2P
c=\frac{2P}{a+b}
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P=\frac{a+b}{2}*c
\frac{a+b}{2}*c=P
\frac{a+b}{2}=\frac{P}{c}
(a+b)*c=2P
ac+bc=2P
ac=2P-bc |:c
a=\frac{2P}{c}-b
Zadanie 2
(-3\sqrt3)^2=(-3)^2*(\sqrt3)^2=9*3=27