Given y=1over 1+x ,find the value of x when y=3

1) y = 1 over 1 + x
3 = 1+x
-x = 1-3
-x = -2
x = 2

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

3) y = 3x over x+2
4(x+2) = 3x
4x+8 = 3x
4x-3x = -8
x = -8

4) y =1+x over 1-x
5(1-x) = 1+x
5-5x = 1+x
5-1 = 5x+x
4 = 6x
x = 4 over 6

Given y=1over 1+x ,find the value of x when y=3

y=1/(1+x)
if y=3,
3=1/(1+x)
3(1+x)=1
1+x=1/3
x=(1/3)-1
x=-2/3

Given y=1over 1+x ,find the value of x when y=4

y=1/(1+x)
if y=4,
4=1/(1+x)
4(1+x)=1
1+x=1/4
x=(1/4)-1
x=-3/4

Given y=3x over x+2 ,find the value of x when y=2

y=3x/(x+2)
if y=2
2=3x/(x+2)
2x+4=3x
4=3x-2x
x=4

Given y=1+x over 1-x ,find the value of x when y=5

y=(1+x)/(1-x)
if y=5,
5=(1+x)/(1-x)
5(1-x)=1+x
5-5x=1+x
5-1=x+5x
4=6x
x=4/6
x=2/3

y = 1/(1+x)
(1+x)y = 1
(1+x) = 1/y
x = 1/y - 1
when y = 3, x = 1/3 - 1 = -2/3

when y = 4, x = 1/4 - 1 = -3/4
-------------------------------------------------
y = 3x /(x+2)
when y = 2,
3x /(x+2) = 2
3x = 2(x+2)
3x = 2x + 4
x = 4
------------------------------------------
y = (1+x)/(1-x)
when y = 5,
(1+x)/(1-x) = 5
(1+x) = 5(1-x)
1 + x = 5 - 5x
1 + 6x = 5
6x = 4
x = 2/3

2007-10-10 20:28:00 補充：
慢左, 做得好辛苦,投我一票啦, 唔該