好簡單既math 10點

1)
12(y-9)=6(y-5)
12y-108=6y-30
12y-6y=108-30
6y=78
y=78/6
y=13
2)
2(-9y-15)=-4(5y+10)
-18y-30=-20y-40
20y-18y=30-40
2y=-10
y=-10/2
y=-5
3)
5(z+1)-8(z-3)=1
(5z+5)-(8z-24)=1
5z-5-8z+24=1
19-3z=1
-3z=1-19
-3z=-18
z=-18/-3
z=6
4)
9(2z-7)+3(-2-12z)=-15
(18z-63)+(-6-36z)=-15
18z-63-6-36z=-15
-18z-69=-15
-18z=-15+69
-18z=54
z=54/-18
z=-3

1.
12(y-9)=6(y-5)
2(y-9) = y-5
2y-18 = y-5
2y-y = 18-5
y = 13

2.
2(-9y-15)=-4(5y+10)
-2(9y+15) = -4(5y+10)
9y+15 = 2(5y+10)
9y+15 = 10y+20
15-50 = 10y-9y
y = -5

3.
5(z+1)-8(z-3)=1
5z+5-8z+24 = 1
5+24-1 = 8z-5z
28 = 3z
z = 28/3

4.
9(2z-7)+3(-2-12z)=-15
3(2z-7)+(-2-15z) = -5
6z-21-2-15z = -5
6z-15z = -5+21+2
-9z = 18
z = 18/(-9)
z = -2

2010-11-04 23:45:41 補充：
SOrry.... #4 睇寫

4.
9(2z-7)+3(-2-12z)=-15
3(2z-7)+(-2-12z) = -5
6z-21-2-12z = -5
6z-12z = -5+21+2
-6z = 18
z = 18/(-6)
z = -3

2010-11-04 23:47:47 補充：
2.
2(-9y-15)=-4(5y+10)
-2(9y+15) = -4(5y+10)
9y+15 = 2(5y+10)
9y+15 = 10y+20
15-20 = 10y-9y <=== 之前寫了 15-50 = 10y-9y
y = -5

1.12(y-9)=6(y-5)
12y-108=6y-30
12y-6y=108-30
6y=78
y=78/6
y=13

2.2(-9y-15)=4(5y+10)
-18y-30=20y+40
-18y-20y=30+40
-38y=70
y=-70/38

3.5(z+1)-8(z-3)=1
5z+5-8z+24=1
5z-8z=1-5-24
-3z=-28
z=28/3

4.9(2z-7)+3(-2-12z)=-15
18z-63+(-6-36z)=-15
18z-63-6-36z=-15
18z-36z=-15+63+6
-18z=54
z=-3

第一題
12y-108=6y-30
12y=6y-30-108
12y+78=6y
78=6y-12y
78=-6y
y=-13
第二題
-18y-10=-20y-40
-18y=-20y-40+10
-18y+20y=-30
2y=-30
y=-15
第三題
5z+5-8z+24=1
-3z+29=1
-3z=-28
z=28/3
第四題
18z-63-6-36z=-15
18z-36z-63-6=-15
-18z-69=-15
-18z=-15+69
-18z=54
z=-3