If a2 - b2 = 10 and a*b = 8, find a4 + b4.  Choose the correct choice.
A) 200  B) 228  C) 182  D) 102  E) 128

Rationale: "a 2 - b 2 = 10 : given a 4 + b 4 - 2 a 2 b 2 = 102 : square both sides and expand . a * b = 8 : given a 2 b 2 = 82 : square both sides . a 4 + b 4 - 2 ( 64 ) = 100 : substitute a 4 + b 4 = 228 correct answer b"
Answer: B