F.2Maths!!!!!!!!!!!20p!!!!!!

1) 3x + 2y = 2... (1)
4x – 3y = -20 … (2)
(1) x 3 => 9x + 6y = 6 … (3)
(2) x 2 => 8x – 6y = -40 … (4)
(3) + (4) => 17x = -34
x = -2
Sub into (1), (3)(-2) + 2y = 2
2y – 6 = 2
2y = 8
y = 4
2) Let x be the larger number and y be the smaller number.
x + y = 53 … (1)
x – y = 5 … (2)
(1) + (2) => 2x = 58
x = 29
Sub into (1), 29 + y = 53
y = 24
The two numbers are 24 and 29

1)
3x+2y=2_________________(1)
4x-3y=-20________________(2)
Form (1),we have
3x=2-2y
x=1/3 (2-2y)_______________________(3)
Subst. (3) into (2),we have
4[1/3 (2-2y)]-3y=-20
4(2-2y)-9y=-60
8-8y-9y=-60
-17y=-68
y=4
Subst. y=4 into (1),we have
3x+2(4)=2
3x+8=2
3x=-6
x=-2

2.Let x be the larger number and y be the smaller number.
x+y=53__________________________(1)
x-y=5___________________________(2)
(1)+(2):2x=58
x=29
Subst. x=29 into (1)
(29)+y=53
y=24


2009-08-27 20:49:16 補充：
慢了...