Question

if x²+1/x²=7 then finx the value of x³+1/x³​

Answer 1

Answer:

the answer is 18

Step-by-step explanation:

if x²+1/x²=7

then

(X+1/X)²=x²+1/x²+2

(x+1/x)=√7+2

(x+1/x)=√9

x+1/x=3

therefore to find (x³+1/x³)

(x+1/x)³=x³+1/x³+3*(X+1/X)

(3)³=x³+1/x³+3(3)

27=x³+1/x³+9

27-9=x³+1/x³

18=x³+1/x³

so

x³+1/x³=18