(1){4s+3t=5,{2s-t=-5;(2){5x-6y=9,{7x-4y=-5.
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![(1){4s+3t=5,{2s-t=-5;(2){5x-6y=9,{7x-4y=-5.](/uploads/image/z/1121880-48-0.jpg?t=%EF%BC%881%EF%BC%89%7B4s%2B3t%3D5%2C%7B2s-t%3D-5%3B%EF%BC%882%EF%BC%89%7B5x-6y%3D9%2C%7B7x-4y%3D-5.)
(1){4s+3t=5,{2s-t=-5;(2){5x-6y=9,{7x-4y=-5.
(1){4s+3t=5,
{2s-t=-5;
(2){5x-6y=9,
{7x-4y=-5.
(1){4s+3t=5,{2s-t=-5;(2){5x-6y=9,{7x-4y=-5.
4s+3t=5①
2s-t=-5②
先用②×2得:4s-2t=-10③
③-①得:(4s-2t)-(4s+3t) =-10-5
-2t-3t=-15
-5t=-15
t=3
把t=3带入②得:2s-3=-5
s=-1
所以,s=-1,t=3
5x-6y=9 ①
7x-4y=-5 ②
①×7得:35x-42y=63 ③
②×5得:35x-20y=-25④
③-④得:(35x-42y)-(35x-20y)= 63-(-25)
-22y = 88
y= -4
把y=4带入①得:5x+24=9
5x = -15
x=-3
所以:x=-3,y=-4