b: \(AB=\sqrt{\left(2+1\right)^2+\left(5-1\right)^2}=5\left(m\right)\)
\(AC=\sqrt{\left(2-3\right)^2+\left(5-1\right)^2}=\sqrt{17}\left(m\right)\)
\(BC=\sqrt{\left(-1-3\right)^2+\left(1-1\right)^2}=4\left(cm\right)\)
\(P=9+\sqrt{17}\left(cm\right)\)
\(S=\sqrt{P\cdot\left(P-AB\right)\cdot\left(P-AC\right)\cdot\left(P-BC\right)}\)
\(=\sqrt{\left(9+\sqrt{17}\right)\left(4+\sqrt{17}\right)\cdot9\cdot\left(5+\sqrt{17}\right)}\)
\(\simeq93,56\left(m^2\right)\)
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