1.8r-11s=12r+13s-56=-652.x+y+z=26①x-y=1②2x-y+z=18③3.2a+5(b-1)=14①3(a-2)-(4b+3)=-15②所有的未知数都要求1.8r-11s=12r+13s-56=-652.x+y+z=26①x-y=1②2x-y+z=18③3.2a+5(b-1)=14①3(a-2)-(4b+3)=-15②所有的未知数都

Question

1.8r-11s=12r+13s-56=-65
2.x+y+z=26 ①
x-y=1 ②
2x-y+z=18 ③
3.2a+5(b-1)=14 ①
3(a-2)-(4b+3)=-15 ②
所有的未知数都要求
1.8r-11s=12r+13s-56=-65
2.x+y+z=26 ①
x-y=1 ②
2x-y+z=18 ③
3.2a+5(b-1)=14 ①
3(a-2)-(4b+3)=-15 ②
所有的未知数都要求

Answer 1

1.8r-11s=-65 (1)
12r+13s=-65+56 (2)
(1)×3-(2)×2 得s=3,r=-4.
2.(1)+(2) 得3x+z=27
(3)-(2) 得x+z=17 x=5,z=12,y=4.
3.2a+5b=19 (1)
3a-4b=-6 (2)
(1)×3-(2)×2 b=3,a=2.