Question

if x-y=4 and xy=21 find x^3-y^3​

Answer 1

Answer:

see the attachment.....

Answer 2

Step-by-step explanation:

x - y = 4

xy = 21

y = 21/x

x - 21/x = 4

x^2 - 4x -21 = 0

(x-7)(x+3) = 0

x = 7 , -3

y = 21/x = 21/7 = 3

y = 21/x = 21/-3 = -7

x,y = (7,3) or (-3,-7)

x^3 - y^3 = (7)^3 - (3)^3 = 343 - 27 = 316