Question

giải pt bằng phương pháp thế

a, {x+5y=9

{-5x-3y=27

b, {8x+5y=32

{4x-6y=19

Answer 1

a: \(\Leftrightarrow\left\{{}\begin{matrix}5x+25y=45\\-5x-3y=27\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}22y=72\\x+5y=9\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{36}{11}\\x=-\dfrac{81}{11}\end{matrix}\right.\)

b: \(\Leftrightarrow\left\{{}\begin{matrix}8x+5y=32\\8x-12y=38\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}17y=-6\\4x-6y=19\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=-\dfrac{7}{17}\\x=\dfrac{281}{68}\end{matrix}\right.\)