Question

6．已知$\left\{\begin{array}{l}{3x-5y=6}\\{x+4y=-15}\end{array}\right.$，則該方程組的解為（　�。�

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

Answer 1

分析 方程組利用加減消元法求出解即可．

解答 解：$\left\{\begin{array}{l}{3x-5y=6①}\\{x+4y=-15②}\end{array}\right.$，
①×4+②×5得：17x=-51，
解得：x=-3，
把x=-3代入②得：y=-3，
則方程組的解為$\left\{\begin{array}{l}{x=-3}\\{y=-3}\end{array}\right.$，
故選D

點評 此題考查了解二元一次方程組，利用了消元的思想，消元的方法有：代入消元法與加減消元法．