Question

If x+y=7 and xy=6 the value of (x³+y³) is.

Answer 1

Good Afternoon

xy = 6

x + y = 7

CUBING on both sides we have

( x + y )³ = 7³

x³ + y³ + 3xy ( x + y ) = 729

x³ + y³ + 3 ( 6 ) ( 7 ) = 729

x³ + y³ = 729 - 126

x³ + y³ = 603

So, x³ + y³ = 603