Question

if x²+1/x = 4 then 2x²+ 2/x³​

Answer 1

Answer:

:x² + 1/x² =4

(x + 1/x)² -2.x.1/x = 4

(x + 1/x )² -2 = 4

(x + 1/x )² = 6

take square root both sides

(x + 1/x) = 4

then,

x³ + 1/x³ = ( x + 1/x)³ - 3.x.1/x(x + 1/x)

= ( x +1/x)³ -3(x + 1/x)

= (4)³ -3(4)

= 64 - 12

= 52