If a2 - b2 = 10 and a*b = 5, find a4 + b4.	Options: A) 50 B) 100 C) 150 D) 92 E) 25
a2 - b2 = 10 : given   a4 + b4 - 2a2b2 = 102 : square both sides and expand.   a*b = 5 : given   a2b2 = 52 : square both sides.   a4 + b4 - 2(25) = 100 : substitute   a4 + b4 = 150   correct answer 150
<result>C</result>
If a2 - b2 = 10 and a*b = 5, find a4 + b4.