Question

0.4x+0.3y=2.4 (x-3)/3=(y+6)/5 求解

Answer 1

0.4x+0.3y=2.4
4x+3y=24 (1)
(x-3)/3=(y+6)/5
两边乘15
5x-15=3y+18
5x-3y=33 (2)
(1)+(2)
9x=57
所以x=29/3
y=(5x-33)/3=46/9

Answer 2

0.4X+0.3y=0.8(x-3) 两边乘以10
4X+3y=8X-24
4x=3y+24
0.8(x-3) =0.2(y+6) 两边除以0.2
4x-12=y+6
4x=y+18=3y+24
y=-3
X=15/4

Answer 3

0.4x+0.3y=2.4 ①
(x-3)/3=(y+6)/5②
①式变为x=(2.4-0.3y)/0.4代入②式中
得，[(2.4-0.3y)/0.4-3]/3=(y+6)/5
5*(6-3y/4-3)=3*(y+6)
30-15y/4-15=3y+18
30-15-18=15y/4+3y
27y/4=-3
y=-12/27
则x=19/3