(1)x+y=15 (2)5x-2(10-x)=6y-3(10-y)+19 解得x=9 (2)5X-2(10-X)=6Y-3(10-Y)+195X-20+2X=6Y-30+3Y+195X+2X-6Y-3Y=19+207X-3Y=39然后该如何把7X-3Y=39代入带(1)X+Y=15里啊?如果不能代入,是不是我上面的哪一步算错
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/25 20:42:28
![(1)x+y=15 (2)5x-2(10-x)=6y-3(10-y)+19 解得x=9 (2)5X-2(10-X)=6Y-3(10-Y)+195X-20+2X=6Y-30+3Y+195X+2X-6Y-3Y=19+207X-3Y=39然后该如何把7X-3Y=39代入带(1)X+Y=15里啊?如果不能代入,是不是我上面的哪一步算错](/uploads/image/z/122375-47-5.jpg?t=%281%29x%2By%3D15+%282%295x-2%EF%BC%8810-x%EF%BC%89%3D6y-3%EF%BC%8810-y%EF%BC%89%2B19+%E8%A7%A3%E5%BE%97x%3D9+%EF%BC%882%EF%BC%895X-2%EF%BC%8810-X%EF%BC%89%3D6Y-3%EF%BC%8810-Y%EF%BC%89%2B195X-20%2B2X%3D6Y-30%2B3Y%2B195X%2B2X-6Y-3Y%3D19%2B207X-3Y%3D39%E7%84%B6%E5%90%8E%E8%AF%A5%E5%A6%82%E4%BD%95%E6%8A%8A7X-3Y%3D39%E4%BB%A3%E5%85%A5%E5%B8%A6%EF%BC%881%EF%BC%89X%2BY%3D15%E9%87%8C%E5%95%8A%3F%E5%A6%82%E6%9E%9C%E4%B8%8D%E8%83%BD%E4%BB%A3%E5%85%A5%2C%E6%98%AF%E4%B8%8D%E6%98%AF%E6%88%91%E4%B8%8A%E9%9D%A2%E7%9A%84%E5%93%AA%E4%B8%80%E6%AD%A5%E7%AE%97%E9%94%99)
(1)x+y=15 (2)5x-2(10-x)=6y-3(10-y)+19 解得x=9 (2)5X-2(10-X)=6Y-3(10-Y)+195X-20+2X=6Y-30+3Y+195X+2X-6Y-3Y=19+207X-3Y=39然后该如何把7X-3Y=39代入带(1)X+Y=15里啊?如果不能代入,是不是我上面的哪一步算错
(1)x+y=15 (2)5x-2(10-x)=6y-3(10-y)+19 解得x=9
(2)5X-2(10-X)=6Y-3(10-Y)+19
5X-20+2X=6Y-30+3Y+19
5X+2X-6Y-3Y=19+20
7X-3Y=39
然后该如何把7X-3Y=39代入带(1)X+Y=15里啊?
如果不能代入,是不是我上面的哪一步算错了啊?
(1)x+y=15 (2)5x-2(10-x)=6y-3(10-y)+19 解得x=9 (2)5X-2(10-X)=6Y-3(10-Y)+195X-20+2X=6Y-30+3Y+195X+2X-6Y-3Y=19+207X-3Y=39然后该如何把7X-3Y=39代入带(1)X+Y=15里啊?如果不能代入,是不是我上面的哪一步算错
第二步右边的-30哪里去了?
应该变成5X-20+2X=6Y-30+3Y+19
7x-20=9y-11
7x-9y=9
把这个式子记做3.
1式乘7,7x+7y=105
把这个式子记做4.
4-3,得16y=96
y=6.所以x=9