Maths 快快快

1.
1 - a = 2a + 1
1 - 1 = 2a + a
0 = 3a
a=0.
2.
2(a-2) = 2a + 2
2a - 4 = 2a + 2.
No solution.
3.
a + 2a = a - 9
2a = -9
a = -9/2 .
4.
3y/8 - (y/8 - 1) = 5/4
3y/8 - y/8 + 1 = 5/4
2y/8 = 5/4 - 1
y/4 = 1/4
y = 1

1) 1-a = 2a+1
1-a+a = 2a+1+a
1 = 3a+1
1-1 = 3a+1-1
0 = 3a
0÷3 = 3a÷3
0 = a
a = 0

2) 2(a-2) = 2a+2
2(a-2) = 2(a+1)
2(a-2)÷2 = 2(a+1)÷2
a-2 = a+1
a-2+2 = a+1+2
a = a+3
a-a = a+3-a
0 = 3???<-----------有得計-_-係咪你打錯問題?

3) a+2a = a-9
3a = a-9
3a-a = a-9-a
2a = -9
2a÷2 = -9÷2
a = -9/2 (2分之-9)


4) 8分之3y - (8分之1 y -1) = 4分之5
8分之3y - (8分之y - 1) = 4分之5
8分之3y - 8分之(y-8) = 4分之5
8分之(3y -(y-8)) = 4分之5
8分之(2y+8) = 4分之5
8分之(2y+8) x 4 = 4分之5 x 4
8分之4(2y+8) = 4分之5 x 4
8分之(8y+32) = 5
8分之(8y+32) x 8 = 5 x 8
8y + 32 = 40
8y + 32 - 32 = 40 - 32
8y = 8
y = 1