If x4 + x2y2 + y4 = 24
x2 + y2 + xy = 6
x3 - y3 = ?
Answer & explanation
Correct answer: option 4
x4 + x2y2 + y4 = 24
x2 + y2 + xy = 6
x4 + x2y2 + y4 = 24
2(x2 + y2) = 10
x2 + y2 = 5
Put in x2 + y2 + xy = 6
5 + xy = 6
xy = 1
If x2 + y2 = 5
then x - y = \(\sqrt {5-2}\)
x - y = \(\sqrt {3}\)
x3 - y3 = (x-y)(x2 + y2 + xy)
\(\sqrt {3}\) × 6
6\(\sqrt {3}\)