數學???algebra

1 ) 5y-6y=0=8x-6y-1 It can be rewriiten as :

5y-6x = 0 ----- 1
8x-6y-1 = 0 -----2

1 * 4 (5y-6x)*4 = 0*4
20y-24x = 0 ---------3

2* 3 (8x-6y-1)*3 = 0*3
24x-18y-3 = 0
24x-18y = 3 --------4

3+4 (20y-24x)+(24x-18y) = 0+3
2y = 3
y = 3/2

substitue y=3/2 into 1

5y-6x = 0
5(3/2) - 6x = 0
15/2 - 6x = 0
15 - 12x = 0
x = 15/12
x = 1.25


2 ) a-b=b-a+15=5b It can be rewriiten as :
a-b = 5b ------1
b-a+15 = 5b --------2
From 1
a = 5b+b
a = 6b --------3
substitute 3 into 2
b-a+15= 5b
b-6b+15 =5b
-5b+15=5b
15 = 10b
b = 1.5
substitute b = 1.5 into 1
a-b = 5b
a-1.5 =7.5
a= 9

^_^

1.
5y-6x=8x-6y-1
5y+6y=8x+6x-1
11y=14x-1
y=(14x-1)/11

5y-6x=8x-6y-1
5y+6y+1=8x+6x
11y+1=14x
(11y+1)/14=x
x=(11y+1)/14

2.
a-b=b-a+15=5b
a-b=5b
a=5b+b
a=6b

a-b=5b
a-b=b-a+15
a+a-15=b+b
2a-15=2b
b=(2a-15)/2
b=a-7.5

1. 5y - 6x = 0 --- (1)
8x - 6y - 1 = 0 --- (2)
(1): 5y = 6x
y = 6x/5
代入(2): 8x - 36x/5 - 1 = 0
40x - 36x - 5 = 0
~跟住自己搵答案~

2.a - b = 5b --- (1)
b - a + 15 = 5b --- (2)
(1): a = 6b
代入(2): b - 6b + 15 = 5b
~跟住自己搵答案~

2007-04-10 20:18:04 補充：
樓上個位, 7.5 - 6x = 0, 跟住點會係 - 6x = 7.5 呀?應該低 6x = 7.5, x = 5/4 = 1.25 無負號!

2007-04-10 20:19:07 補充：
上面第二句開頭個度係「應該(係)」

1. 5y-6x=0=8x-6y-1
{5y-6x=0.........(1)
{8x-6y-1=0......(2)
從(2), -6y+8x=1........(3)
(1)*4　20y-24x=0.....(4)
(3)*3　-18y+24x=3.......(5)
－－－－－－－－－－－－－
(4)+(5)　　　2y=3
　　　　　　　y=1.5
把y=1.5代入方程(1)，
5(1.5)-6x=0
7.5-6x=0
-6x=7.5
x=-1.25

2. a-b=b-a+15=5b
{a-b=5b.......(6)
{b-a+15=5b......(7)
化簡，得
{0+a=6b......(8)
{15-a=4b......(9)
(8)　0+a=6b
(9)　15-a=4b
－－－－－－－－
(8)+(9)15=10b
　　　　b=1.5
把b=1.5代入方程(6)，
5(1.5)=a-1.5
7.5=a-1.5
a=9