<s>[INST] Are there any integers $a,b$ s.t. ${ a }^{ 2 }-{ b }^{ 2 }=8$? For $a$ and $b$ are integers greater than $1$, ${ a }^{ 2 }-{ b }^{ 2 }=8$ holds? 
 [/INST] Hint: We have $8= a^2 - b^2 = (a+b)(a-b)$. As $a,b \ge 1$, we have $a+b > a-b$, that is either $a+b=8$ and $a-b = 1$, or $a+b=4$ and $a-b=2$.
</s>