Question

9．用加减消元法解方程组$\left\{\begin{array}{l}{3x-2y=2}\\{x+y=5}\end{array}\right.$，下列变形正确的是（　　）

• A． $\left\{\begin{array}{l}{3x-y=2}\\{x+2y=5}\end{array}\right.$
• B． $\left\{\begin{array}{l}{3x-2y=2}\\{x+2y=5}\end{array}\right.$
• C． $\left\{\begin{array}{l}{3x-2y=2}\\{3x+3y=15}\end{array}\right.$
• D． $\left\{\begin{array}{l}{3x-2y=2}\\{2x+2y=5}\end{array}\right.$

Answer 1

分析 方程组利用加减消元法变形得到结果，即可作出判断．

解答 解：用加减消元法解方程组$\left\{\begin{array}{l}{3x-2y=2}\\{x+y=5}\end{array}\right.$，下列变形正确的是$\left\{\begin{array}{l}{3x-2y=2}\\{3x+3y=15}\end{array}\right.$，
故选C

点评 此题考查了解二元一次方程组，利用了消元的思想，消元的方法有：代入消元法与加减消元法．