Any help would be greatly appreciated.

1. When an expression f(x) is divided by 3x+1, the quotient is 2x-3 and the remainder is x+5. What is f(x)?

2. Factor the following:

(a) x^12n - y^20n

(b) x^2 + 4xy +4y^2 - m^2 - 6mn - 9n^2 [EDIT - SOLVED?]: (x+2y)^2 - (m+3n)^2

(c) 1/3x^-3 y^6 -1/4x^4y^3