Question

6．下列各對(duì)數(shù)中，是二元一次方程3x-y=-7的解的是（　�。�

• A． $\left\{\begin{array}{l}{x=1}\\{y=4}\end{array}\right.$
• B． $\left\{\begin{array}{l}{x=2}\\{y=3}\end{array}\right.$
• C． $\left\{\begin{array}{l}{x=-1}\\{y=4}\end{array}\right.$
• D． $\left\{\begin{array}{l}{x=-2}\\{y=-3}\end{array}\right.$

Answer 1

分析 將每一對(duì)x與y的值分別代入方程3x-y=-7，使方程左右兩邊相等的未知數(shù)的值即為二元一次方程3x-y=-7的解．

解答 解：A、把$\left\{\begin{array}{l}{x=1}\\{y=4}\end{array}\right.$代入方程3x-y=-7，左邊=3-4=-1≠右邊，則$\left\{\begin{array}{l}{x=1}\\{y=4}\end{array}\right.$不是方程3x-y=-7的解；
B、把$\left\{\begin{array}{l}{x=2}\\{y=3}\end{array}\right.$代入方程3x-y=-7，左邊=6-3=3≠右邊，則$\left\{\begin{array}{l}{x=2}\\{y=3}\end{array}\right.$不是方程3x-y=-7的解；
C、把$\left\{\begin{array}{l}{x=-1}\\{y=4}\end{array}\right.$代入方程3x-y=-7，左邊=-3-4=-7=右邊，則$\left\{\begin{array}{l}{x=-1}\\{y=4}\end{array}\right.$是方程3x-y=-7的解；
D、把$\left\{\begin{array}{l}{x=-2}\\{y=-3}\end{array}\right.$代入方程3x-y=-7，左邊=-6+3=-3≠右邊，則$\left\{\begin{array}{l}{x=-2}\\{y=-3}\end{array}\right.$不是方程3x-y=-7的解．
故選C．

點(diǎn)評(píng) 本題考查了二元一次方程的解的定義：一般地，使二元一次方程兩邊的值相等的兩個(gè)未知數(shù)的值，叫做二元一次方程的解．