3x+2y-4z=9,(1) 3x+5y-5z=14(2) 3x-4y+2z=3(3)

问题描述:

3x+2y-4z=9,(1) 3x+5y-5z=14(2) 3x-4y+2z=3(3)
3x+2y-4z=9,(1)
3x+5y-5z=14(2)
3x-4y+2z=3(3)
适合用( 可用(2)-( ),(3)-( ),得到一个含y,z的二元一次方程组.

3x+2y-4z=9,(1)3x+5y-5z=14 (2)3x-4y+2z=3 (3)解(2)-(1)得:3y -z = 5 (4)(2) - (3) 得 :9y -7z = 11 (5)(4)×3 -(5)得:4z = 4 解得:z = 7把z=7代入(4)得 3y = 5 + z,y = (5+z)/3 = (5+7)/3 = 4把...