(a)Determine the number of degrees the axis must be rotated to eliminate the xy term of the conic x2+6xy+y2-6=0.

Question

tan2θ = B/(A-C)

how do I answer the question?

Answer 1

Huh? Use your numbers:

cot2? = (1-1)/6 = 0

2? = 90°
? = 45°

http://www.wolframalpha.com/input/?i=x%5E2%2B6xy%2By%5E2-6%3D0