Question

4(x-y-1)=3(1-y)-2 2/x+3/y=2 的二元一次方程的解为?

Answer 1

4(x-y-1)=3(1-y)-2 ==> 4x-4y-4=3-3y-2 ==> y=4x-5
代入得：2/x+3/(4x-5)=2
2(4x-5)+3x=2x(4x-5)
8x-10+3x=8x^2-10x
8x^2-21x+10=0
(x-2)(8x-5)=0
x=2或x=5/8
y=4x-5=3或y=4x-5=-5/2
所以有两组解x=2,y=3；或x=5/8,y=-5/2

Answer 2

如图所示。

Answer 3

4(x-y-1)=3(1-y)-2 4x-4y-4=3-3y-2 4x-y=5 y=4x-5
2/x+3/y=2 2/x+3/(4x-5)=2
2(4x-5)+3x=2x(4x-5)
8x-10+3x=8x²-10x
8x²-10x-8x-3x=-10
8x²-21x=-10
x²-21x/8=-5/4
x²-21x/8+(21/16)²=441/256-320/256
(x-21/16)²=121/256
x-21/16=±11/16
x=21/16±11/16
x1=21/16+11/16=32/16=2
x2=21/16-11/16=10/16=5/8

Answer 4

X1=2,X2=5/8