Question

10道二元一次方程并解

Answer 1

)9x-12y=33
14x+12y=-102
9x+14x=33-102
x=-3 y=-5

(2)2x+y/6=6
-x+9y=2
-2x+18y=4
y+108y=60
x=324/109 y=60/109

(3)0.4x+0.75y=99
4x+7.5y=990
4x+4y=640
3.5y=350
x=60 y=100

(4)3x=4y
x-3x=5
-2x=5
x=-5/2 y=-15/8

{5a+4b=15 ①
{2a -3b=1 ②
由①×2，②×5得
{10a+8b=30 ③
{10a-15b=5 ④
由③-④得
23b=25
b=25/23
a=9/23

1.－6x+12y=72
2.-4x-6y+=-24
2式乘以2得3式：-8x-12y=-48
1式与3式相加得：
-6x+12y+(-8x-12y)=72+(-48)
则：-14x=24
x=-12/7
所以y=48/7

2x+3y=2 (1)
5x+2y=2 (2)
(2)*3-(1)*2

11x=2
x=2/11
y=6/11

9/5(x+y)=18

x+y=10代入
2/3x+3/2(x+y)=18
2/3x+15=18

2/3x=3
x=9/2
y=11/2