B4:Giải hệ pt:
a)\(\left\{{}\begin{matrix}4x+2y=14\\2x-2y=4\end{matrix}\right.\)
b)\(\left\{{}\begin{matrix}2x-4y=0\\3x+2y=8\end{matrix}\right.\)
c)\(\left\{{}\begin{matrix}2\left(x+y\right)+3\left(x-y\right)=4\\\left(x+y\right)+2\left(x-y\right)=5\end{matrix}\right.\)
d)\(\left\{{}\begin{matrix}\dfrac{1}{x}+\dfrac{1}{y}=\dfrac{1}{12}\\\dfrac{8}{x}+\dfrac{15}{y}=1\end{matrix}\right.\)