代入法(含分數)數條

1.if a=3, 3=1+b ,b=2
2.if a=4, 4=1-b , b=-3
3.if a=2, 2=3b+b,2=4b..b=1/2
4.ifZ=5, x=-4
5.if X=8, 24=3Z+8 Z=...

1. a=1/1+b
a-1=b
3-1=b
2=b
b=2

2. a=1/1-b
4=1-b
4+b=1-b+b
4+b=1
4+b-4=1-4
b=(-3)

3. a=3b/1+b
2=3b+b
2=4b
2/4=4b/4
0.5=b
b=0.5

4. X=1+Z/1-Z
X=1+5/1-5
X=6/(-4)
X=(-1.5)

5. 3X=4Z+X/1-Z
24=4Z+8/1-Z
跟住唔識,但係答案該是0.57145左右

1.
3 = 1 / (1+b)
1+b = 1/3
b = 1/3 -1 = -2/3

2.
4 = 1 / (1-b)
1-b = 1/4
-b= 1/4 -1= -3/4
b=3/4

3.
2 = 3b / (1+b)
1+b = 3b/2
b - 3b/2 = -1
-b/2 = -1
b=2

4. I know you typed something wrong in your question. Please check. My guess it that your question is 己知X=1+Z/1-Z。若X (you typed Z) =5，求Z的值
5 = (1+Z)/(1-Z)
5 (1-Z) = (1+Z)
5 - 5Z = 1 + Z
4 = 6Z
Z = 4/6 = 2/3
Please forgive if I guessed wrong your question.


5. You sure you typed the question correctly? This one involve power of 2 (or square).. We use the sign ^ to stand for the power of
3*5=4Z + 8 / (1-Z)
15 - 4Z= 8 / (1+Z)
(15-4Z) (1+Z) = 8
15+z-4z-4Z^2=8
7-3Z-4Z^2=0
4Z^2 +3Z -7 = 0
(4z + 7) (z-1) = 0
so 4z+7 = 0 or z-1 = 0
4z-7=0
4z=7
z=7/4

or z-1 = 0
z=1


Please let me know what Form are you in !!! (if possible) Thank you.

1.己知a=1/1+b。若a=3，求b的值

3 = 1 / (1 + b)
1 + b = 1/3
b = 1/3 - 1 = -2/3

2.己知a=1/1-b。若a=4，求b的值

4 = 1 / (1-b)
1-b = 1/4
b = 1- 1/4=3/4

3.己知a=3b/1+b。若a=2，求b的值

2 = 3b / (1+b)
2(1+b) = 3b
2 + 2b = 3b
2 = b
b = 2

4.己知X=1+Z/1-Z。若Z=5，求Z的值

5 = (1+Z) / (1-Z)
5 - 5Z = 1 + Z
5 - 1 = 5Z + Z
6Z = 4
Z = 4/6 = 2/3


5,己知3X=4Z+X/1-Z。若X=8，求Z的值

3X=(4Z+X)/(1-Z)
3*8 = (4Z + 8) / (1 - Z)
24 * (1-Z) = 4Z + 8
24 - 24Z = 4Z + 8
24 - 8 = 24Z + 4Z
16 = 28Z
Z = 16/28 = 4/7

1.
a=1/(1+b)
3(1+b)=1
b=(1/3)-1
=-2/3

2.
4=1/(1-b)
4-4b=1
b=-3/4

3.
2=3b/(1+b)
2+2b=3b
b=2

4.
5=(1+Z)/(1-Z)
5-5Z=1+Z
6Z=4
Z=2/3

5.
3(8)=4Z+8/(1-Z)
(6-Z)(1-Z)=2
6-7Z+(Z)^2=2
(Z)^2-7Z+4=0
Z=6.372
OR
Z=0.627