Could someone help me with these induction questions? I only need the bit on proving

n=k+1 using the assumption n=k

Prove:

1^3 + 2^3 + 3^3 +....+n^3 = (1+2+3+...+n)^2 for n = 1,2,3...

1-2+3-4...+n(-1)^(n+1) = 1/4[1 - (2n+1)(-1)^n] for n = 1,2,3...

5/(1.2.3) + 6/(2.3.4) +7/(3.4.5) +...+(n+4)/n(n+1)(n+2) = [n(3n+7]/[2(n+1)(n+2)]

Thank you ! =)