Simplify: 81 X 81 + 68 X 68-2 x 81 X 68.  Choose the correct choice from the following:
A) 169	B) 159	C) 189	D) 179	E) 219

Rationale: = ( 81 ) ^ 2 + ( 68 ) ^ 2 – 2 x 81 x 68 = a ^ 2 + b ^ 2 – 2 ab , where a = 81 , b = 68 = ( a - b ) ^ 2 = ( 81 – 68 ) ^ 2 = ( 13 ) ^ 2 = 169 . answer is a .
Answer: A