Question

if x-y=4 and xy=21 then x³-y³=​

Answer 1

Answer:

21 is 7 x 3

4 is 7 - 3

So, let x be 7 and y be 4

(7)^3 - (4)^3

343 -64

279

Answer 2

Answer:

316

Step-by-step explanation:

x-y=4 xy=21

x=21/y

putting x's value in first equation

21/y-y=4

21/y=4+y

21=y(4+y)

0=y sq. +4y -21

using sridharacharya's method we get roots for y value

as,  y=3 or y= -7

as root is equal and real y=3

hence x=7

343 - 27 =316