Question

二元一次方程{3（x-2）+4y=2y-1①{2x+5y=7②

Answer 1

3(x-2)+4y=2y-1

3x+2y=5

2x+5y=7

6x+4y-6x-15y=10-21

-11y=-11

y=1

3x+2=5

3x=3

x=1

(2) x/2+1/3-y=1 3x-6y=4

3x++2y=10

3x+2y-3x+6y=10-4

8y=6 y=3/4

3x+3/2=10 x=17/6

(3)0.8x-0.9y=2 8x-9y=20

6x-3y=2.5

8x-9y-18x+9y=20-7.5

-10x=-12.5

x=5/4

15/2-3y=2.5

y=5/3