simp
case zero
ih : ∑ i ∈ Finset.range 0, i ^ 3 = (∑ i ∈ Finset.range 0, i) ^ 2
h1 : (∑ x ∈ Finset.range 0, x + 0) ^ 2 = (∑ x ∈ Finset.range 0, x) ^ 2 + ((2 * ∑ x ∈ Finset.range 0, x) * 0 + 0 ^ 2)
h5 : 2 * ∑ x ∈ Finset.range 0, x = (∑ x ∈ Finset.range 0, x) * 2
⊢ 0 ^ 3 = 0 * (0 - 1) * 0 + 0 ^ 2
no goals