form 4 maths

simplify the following expressions
1) 2^(y-1)+2^(y+2)/9
2) 6^(2x)/4^(x)X3^2 <X係乘
3) (2a^3-2x/5a^4x-1)^-2


4) make b the subject of the formula c=ab/a+b


factorize the following expressions
5) a^2(b+1)^2-16
6) (b-1)^2-10(b-1)+25
7) (2a+b)(2a-b)-4a+1
8) a^3+b^3-a^2b-ab^2