Question

[Nguyễn Khánh Linh]

Bài 2 : giải hệ phương trình

a , \(\left\{{}\begin{matrix}3x-4y=2\\-5x-3y=4\end{matrix}\right.\)

b , \(\left\{{}\begin{matrix}2x-3y+2z=4\\-4x+2y+5z=-2\\2x+5y+3z=8\end{matrix}\right.\)

Answer 1

[Nguyễn Việt Lâm]

a/ \(\Leftrightarrow\left\{{}\begin{matrix}15x-20y=10\\-15x-9y=12\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}-29y=22\\x=\frac{4y+2}{3}\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}y=-\frac{22}{29}\\x=-\frac{10}{29}\end{matrix}\right.\)

b/ \(\Leftrightarrow\left\{{}\begin{matrix}2x-3y+2z=4\\-4y+9z=6\\8y+z=4\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}2x-3y+2z=4\\-4y+9z=6\\19z=16\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}z=\frac{16}{19}\\y=\frac{15}{38}\\x=\frac{7}{4}\end{matrix}\right.\)