question No5 and 7

2 f) Explain why these steps show that this formula is true whenever n is a positive integer. 5. Prove that 12 +32+52 ++(2n+1)2-(n+ 1) (2n +1)(2n +3)/3 whenever n is a nonnegative integer. 6. Prove that 1.11+2-2! + +n.n! = (n + 1)!--1 step of whenever n is a positive integer. 7. Prove that 3 + 3-5 + 3-52+-.. +3 . 5-3 (5n +1-|)/4 ? whenever n is a nonnegative integer. 8. Prove that 2-2-7 + 2-72-, it +2(-7)": (L- re you 7)n+1)/4 whenever n is a nonnegative integer