(Please read "Edit"s and see this.)
How could I prove that : $\text{If} \space m^2=a^3-b^3\text{ where}\space m,a,b\in\mathbb{N} \rightarrow \exists c,d \in\mathbb{N}\space \text{ such that}\space m=c^2+d^2 $ thanks for helping
Edit: I told the person who gave me this question it's wrong, and he corrected it like this: $\text{If} \space m^2=(a+1)^3-a^3\text{ where}\space m,a\in\mathbb{N} \rightarrow \exists c,d \in\mathbb{N}\space \text{ such that}\space m=c^2+d^2 $ It's such an easy question and I already know the answer.
Edit2:I though I know this question answer but after thinking I can't solve this, could any one help me to figure out how to solve this?(I hope it wasn't wrong like previous question, but if you think it's wrong please let me know,I need to solve this question for exam I wanna take from my students.)
Edit 3: the second question wasn't wrong and has been answered at this link.