Question

13．已知$\left\{\begin{array}{l}{x=2}\\{y=-1}\end{array}\right.$與$\left\{\begin{array}{l}{x=3}\\{y=-\frac{1}{2}}\end{array}\right.$是關(guān)于xy的二元一次方程y=kx+b的解，則k，b的值是（　�。�

• A． k=1，b=2
• B． k=$\frac{1}{2}$，b=-2
• C． k=2，b=-$\frac{1}{2}$
• D． k=-2，b=$\frac{1}{2}$

Answer 1

分析 把x與y的兩對值代入方程計算求出k與b的值．

解答 解：把$\left\{\begin{array}{l}{x=2}\\{y=-1}\end{array}\right.$與$\left\{\begin{array}{l}{x=3}\\{y=-\frac{1}{2}}\end{array}\right.$代入方程得：$\left\{\begin{array}{l}{2k+b=-1}\\{3k+b=-\frac{1}{2}}\end{array}\right.$，
解得：$\left\{\begin{array}{l}{k=\frac{1}{2}}\\{b=-2}\end{array}\right.$，
故選B

點評 此題考查了二元一次方程的解，方程的解即為能使方程左右兩邊相等的未知數(shù)的值．