3x+6y=165和6x+3y=150.二元一次方程和一元一次方程,
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3x+6y=165和6x+3y=150.二元一次方程和一元一次方程,
3x+6y=165和6x+3y=150.二元一次方程和一元一次方程,
3x+6y=165和6x+3y=150.二元一次方程和一元一次方程,
3x+6y=165
6x+3y=150
相加
9x+9y=315 x+y=35 (1)
相减
3x-3y=-15 x-y=-5 (2)
(1)+(2) 2x=30 x=15 y=20
2(3x+6y=165)-(6x+3y=150)得9y=180 y=20
3x+6*20=165 x=15
(1)3x+6y=165
(2)6x+3y=150
(1)*2=(3) : 6x+12y=330
(3)-(2) : 9y=180 y=20
6x+3*20=150 6x=90 x=15
x=15 ; y=20
2×(3x+6y)=2×165 →6x+12y=330 (1)
6x+3y=150 (2)
(1)减去(2)得:9y=180
y=20
将y=20代入方程(2)得:6x+3×20=150
x=15
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