If a2 - b2 = 10 and a*b = 8, find a4 + b4.
Answers:	A) 200	B) 228	C) 182	D) 102	E) 128
a2 - b2 = 10 : given   a4 + b4 - 2a2b2 = 102 : square both sides and expand.   a*b = 8 : given   a2b2 = 82 : square both sides.   a4 + b4 - 2(64) = 100 : substitute   a4 + b4 = 228   correct answer 228
<result>B</result>
If a2 - b2 = 10 and a*b = 8, find a4 + b4.