If x3 + y3 = 152
x + y = 8
Find the value of x4 + y4 + 14.
Answer & explanation
Correct answer: option 3
x3 + y3 = 152
x + y = 8
(x + y)3 = x3 + y3 + 3xy (x + y)
512 = 152 + 24xy
xy = \(\frac{360}{24}\)
xy = 15
⇒ x2 + y2 = 64 - 2 × 15
⇒ x2 + y2 = 34
⇒ x4 + y4 = (34)2 - 2 × 15 × 15
⇒ x4 + y4 = 1156 - 450 = 706
x4 + y4 + 14 = 706 + 14
= 720