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Ramesh2007
- Junior | Next Rank: 30 Posts
- Posts: 20
- Joined: Sun Apr 15, 2007 11:54 pm
a^4 - b^4 = (a^2 + b^2) * (a^2 - b^2)
1 - insufficient. We don't know a^2+b^2
2 - insufficient. Again, we don't know a^2+b^2
1 and 2 together gives you
a^2 - b^2 = 16
(a+b)*(a-b) = 16
8*(a-b) = 16
a-b = 2, a+b = 8. We can solve for a and b and hence we can get
a^4 - b^4
So, C
