If f(x) = x^2, find f(8-square root 5)
=(8-sq. root 5)(8- sq. root 5)
=8^2-8(sq. root 5)-8(sq. root 5)+(sq. root 5)^2
=64-16 sq. root 5+5
=64+5-16 sq. root 5
=69-16 square root 5