Question

If x+y=7 ,xy=10 then find 1/x3+1/y3

Answer 1

Answer:

The value of 1/x³ + 1/y³ = 133/1000  

Step-by-step explanation:

Given : x+y = 7 and xy = 10

           1/x³ + 1/y³ = ?

Solution : 1/x³ + 1/y³ = ( x³ + y³)/x³y³ ----------1

x³ + y³ = (x+Y)³ - 3xy(x+y)

            = 7³ - 3x10x7

           = 343-210

           = 133 ----------2

Substituting 2 in 1 ,we get

1/x³ + 1/y³ = ( x³ + y³)/(xy)³

               = 133/10³  

                = 133/1000