<p>this question looks really easy but I can't seem to get it right, can you guys help? thanks.</p>
<p>if a and b are integers and a power 2 - b power 2 = 7, what's the value of a?</p>
<p>A 3
B 4
C 5
D 6
E 7</p>
<p>I thinks its B. Try plugging in the answers. If you put 7 then , 7^2 - b^2 wont be 7 because , 49 - power of next integer (6^2) =13. If you keep on doing so , you'll get 11 for D, 9 for C , and 7 for B.</p>
<p>I'm not that good at explaining.</p>
<p>that sounds about right. But is there a way to do it mathematically?</p>
<p>a^2 - b^2 = (a+b)(a-b)
If a and b are both integers, then (a+b), (a-b) are also integers
If the product of two integers is 7, then the integers are (7,1) or (-7,-1)
The (7,1) answer is simpler, from which a+b = 7, a-b = 1
Therefore, a=4, b=3 is one possible answer.</p>
<p>(The other possible answer is a=-4, b=-3)</p>
<p>yes plugging in gives you choice B; 4. That's how i did</p>
<p>wow, I never even thought of the a+b, a -b thing. Now I get it.
Thanks guys....</p>