Question

bằng phương pháp thế , giải các hệ phương trình sau rồi tính nghiệm gần đúng chính xác đến hai số thập phân

a,\(\left\{{}\begin{matrix}x-\sqrt{3}y=0\\\sqrt{3}x+2y=1+\sqrt{3}\end{matrix}\right.\)

b,\(\left\{{}\begin{matrix}\sqrt{2}x-\sqrt{5}y=1\\x+\sqrt{5}y=\sqrt{2}\end{matrix}\right.\)

c,\(\left\{{}\begin{matrix}\sqrt{2}x+\sqrt{5}y=2\\x+\sqrt{5}y=2\end{matrix}\right.\)

d,\(\left\{{}\begin{matrix}x-2\sqrt{2}y=\sqrt{3}\\\sqrt{2}x+y=1-\sqrt{6}\end{matrix}\right.\)

Answer 1

Làm mẫu hai câu a, b thôi nha.

a, \(\left\{{}\begin{matrix}x-\sqrt{3}y=0\\\sqrt{3}x+2y=1+\sqrt{3}\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=\sqrt{3}y\\\sqrt{3}.\sqrt{3}y+2y=1+\sqrt{3}\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=\sqrt{3}y\\5y=1+\sqrt{3}\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{\sqrt{3}+3}{5}\\y=\dfrac{1+\sqrt{3}}{5}\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x\approx0,95\\y\approx0,55\end{matrix}\right.\)

b, \(\left\{{}\begin{matrix}\sqrt{2}x-\sqrt{5}y=1\\x+\sqrt{5}y=\sqrt{2}\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}\sqrt{2}\left(\sqrt{2}-\sqrt{5}y\right)-\sqrt{5}y=1\\x=\sqrt{2}-\sqrt{5}y\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}2-\sqrt{5}\left(\sqrt{2}+1\right)y=1\\x=\sqrt{2}-\sqrt{5}y\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{\sqrt{2}-1}{\sqrt{5}}\\x=1\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}y\approx0,19\\x=1\end{matrix}\right.\)