Đáp án:
5) x=6
6) a)(x;y)=(10;7)
b) (x;y;z)=(10;3;6)
Giải thích các bước giải:
\(
\begin{array}{l}
1)\sqrt {2x - 3} = x - 3 \\
Đk:x \ge 3 \\
\Leftrightarrow 2x - 3 = (x - 3)^2 \\
\Leftrightarrow x^2 - 6x + 9 = 2x - 3 \\
\Leftrightarrow x^2 - 8x + 12 = 0 \\
\Leftrightarrow \left[ {\begin{array}{*{20}c}
{x = 2(ktm)} \\
{x = 6(tm)} \\
\end{array}} \right. \\
2) \\
a)\left\{ {\begin{array}{*{20}c}
{x - y = 3} \\
{3x - 4y = 2} \\
\end{array}} \right. \Leftrightarrow \left\{ {\begin{array}{*{20}c}
{x = y + 3} \\
{3(y + 3) - 4y = 2} \\
\end{array}} \right. \\
\Leftrightarrow \left\{ {\begin{array}{*{20}c}
{x = y + 3} \\
{y = 7} \\
\end{array}} \right. \Leftrightarrow \left\{ {\begin{array}{*{20}c}
{x = 10} \\
{y = 7} \\
\end{array}} \right. \\
b)\left\{ {\begin{array}{*{20}c}
{4y = 12} \\
{y + 2z = 15} \\
{x + y - z = 7} \\
\end{array}} \right. \Leftrightarrow \left\{ {\begin{array}{*{20}c}
{y = 3} \\
{3 + 2z = 15} \\
{x + 3 - z = 7} \\
\end{array}} \right. \Leftrightarrow \left\{ {\begin{array}{*{20}c}
{y = 3} \\
{z = 6} \\
{x = 10} \\
\end{array}} \right. \\
\end{array}
\)
