Chép bài mệch mũi =((

\(P=\dfrac{U^2}{R}=\dfrac{220^2}{48,4}=1000\left(W\right)\)

\(S_{ABC}=\dfrac{1}{2}AB.AC=\dfrac{1}{2}.8.9=36\left(cm^2\right)\)

Huhu bn đó ms sửa đề á trùi =))

\(\Rightarrow\left[{}\begin{matrix}2x=0\\x-\dfrac{1}{7}=0\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{7}\end{matrix}\right.\)