拓展:1，已知:｛3x+y+2z=285x-3y+z=7求:x+y+z的值

更新时间2022-02-27 06:07:49

3x + y + 2z =28；①

①乘以3，9x + 3y + 6z = 84； ②

5x - 3y + z =7； ③

③ + ②，14x + 7z = 91，除以7，2x + z = 13； ④

③ 乘以2，10x - 6y + 2z = 14；⑤

⑤ - ①，7x - 7y = -14，除以7，x - y = -2；⑥

④ - ⑥，x + y + z = 15 。