中一的數學題

4) 2a=7a+30

2a=7a+30
2a - 7a = 30
-5a = 30
a = 30/ (-5)
a = -6

6) 4.2n=6n-9

4.2n=6n-9
4.2n - 6n = -9
-1.8n = -9
n = -9/(-1.8)
n = 5

8) 2(z+1)=3(z-4)

2(z+1)=3(z-4)
2z + 2 = 3z - 12
2z - 3z = -12 - 2
-z = -14
z = 14

10) 2x=3(1-x)-(x+1)

2x=3(1-x)-(x+1)
2x = 3 - 3x - x - 1
2x = 2 - 4x
2x + 4x = 2
6x = 2
x = 2/6
x= 1/3

16) 6[2(2-y)-3y]=24

6[2(2-y)-3y]=24
6(4 - 2y - 3y) =24
4 - 5y = 24/6
4 - 5y = 4
-5y = 4 - 4
-5y = 0
y = 0

28) 3份之1(t+9)=3份之1-0.5(t+3)

3份之1(t+9)=3份之1-0.5(t+3)
1/3 乘 (t + 9) = 1/3 - 0.5(t + 3)
3 乘 [1/3 乘 (t + 9)] = 3 乘 [1/3 - 0.5(t + 3)]
t + 9 = 1 - 1.5(t + 3)
t + 9 = 1 - 1.5t - 4.5
t + 9 = -3.5 - 1.5t
t + 1.5t = -3.5 - 9
2.5t = -12.5
t = -12.5/2.5
t = -5

希望幫到你

4) 2a=7a+30
2a-7a=30
-5a=30
a=-6

6) 4.2n=6n-9
4.2n-6n=-9
-1.8n=-9
n=5

8) 2(z+1)=3(z-4)
2*3*(z+1)=z-4
6z+6=z-4
6z+10=z
5z=-10
z=-2

10) 2x=3(1-x)-(x+1)
2x+(x+1)=3-3x
2x=3-3x-x-1
6x=2
x=2/6
x=1/3

16)6[2(2-y)-3y]=24
2(2-y)-3y=24/6
4-2y=4+3y
4=4+5y
0=5y
0=y
y=0

28) 3份之1(t+9)=3份之1-0.5(t+3)
3份之1t+3=3份之1-2份之1t-1.5
3份之1t+2份之1t=3份之1-1.5-3
6份之5t=30份之10-30份之135
6份之5t=30份之125
6份之5t=-6份之25
5t=-25
5t=-5

28)
1/3(t+9)=1/3-0.5(t+3)
2(t+9)=2-3(t+3) <------整條式乘6
2t+18=2-3t-9
2t+3t=2-9-18
5t=-25
t=-5

4)2a=7a+30
-5a=30
a=-6

8) 2(z+1)=3(z-4)
2z+2=3z-12
-z=-14
z=14

10)2x=3(1-x)-(x+1)
2x=3-3x-x-1
6x=2
x=1/3