Question

if x-y=4 and xy=45. Find x3-y3

Answer 1

x=4-x,y=4-x
(4+y)3-(4-x)3=0
12+3y-12-3x=0
3y-3x=0
3(y-x)=0
y-x=0

Answer 2

Answer:

604

Step-by-step explanation:

X-Y = 4

Squraing both sides

X^2 + Y^2 - 2XY = 16

XY = 45

X^2 + Y^2 - 90 = 16

X^2 +Y^2 = 106

(X+Y)^2 = X^2 + Y^2 + 2XY

(X+Y)^2 = 106 + 90

(X+Y)^2 = 196

X+Y = +/-14

X-Y = 4

X= 9 , -5

Y= 5, -9

X^3 - Y^3

= 9^3 -5^3 = 729-125=604

= (-5)^3 - (-9)^3 = -125 + 729 = 604