if x+y =6 xy=2 find x3 -y3
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(x+y)^2 = x^2 + y^2 +2 xy
36= x^2 + y^2 + 4
x^2 + y^2 = 32
(x-y)^2 = x^2 + y^2 - 2xy
= 32 - 4
(x-y)^2 = 28 = > x-y = 2 √7
x^3 - y^3 = (x-y)(x^2 + y^2 + xy)
=(2√7) x ( 2 + 32 )
= 2 x 34 x √7
= 68 x√7
= 68 x 2.465 = 167.62
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