Question

if x³+y³=1120 and x+y= 10 then find xy

Answer 1

Formula:

(x+y)whole cube=x cube +y cube +3xy(x+y)

putting the given values,

(10)cube=1120+3xxy(10)

1000=1120+30xy

1000-1120=30xy

-120=30xy

-120/30=xy

-4=xy

Verification:

putting the value of xy,

1000=1120+30(-4)

1000=1120+(-120)

1000=1120-120

1000=1000

Proved that the value of xy is equal to -4