For how many unique pairs of nonnegative integers {a, b} is the equation a^2 - b^2 = 220 true?	Choose the correct choice from the following options:  A) 1  B) 3  C) 5  D) 6  E) 9
Answer 6   (a+b)(a-b)=220   6cases For (a+b), (a-b)   220, 1   110, 2   55, 4   44,5   22, 10   20,11   Answer 6
<result>D</result>
For how many unique pairs of nonnegative integers {a, b} is the equation a^2 - b^2 = 220 true?