2. Use the formal definitions of ,O and to prove the following: (a) (1.5 pt) f(n)=n2+2n+5(n2) (b) (1.5 pt) f(n) =i=1n((i1)i)(n3) For (b), you will need a formula for the sum of the squares of the first n positive integers: https://www. cuemath.com/algebra/sum-of-squares/