Question

20. If x + (1/x) = 5, then the value
of x3 + (1/x3) is
O 140
O 125
O 110
O 150
Required
21

Answer 1

Answer:

110

Step-by-step explanation:

x+1/x=5

cubing both side

we get

(a+b)³=a³+b³+3ab(a+b)

x³+1/x³+3(x+1/x)=5³

x³+1/x³+3(5)=125

x³+1/x³=125-15

=110