Question

if x-y=2 and xy=15 then x^3-y^3 is?​

Answer 1

Same

Answer

Guy

Step-by-step explanation:

given,

x-y = 2

cubing both sides

(x-y)³ = 2³

=> x³- y³ -3xy ( x-y) = 8

=> x³ - y³ - 3×15×2= 8.

=> x³ - y³ - 90 = 8

=>x³ - y³ = 8+90

=> x³ - y³ = 98

Answer 2

Answer:

x³-y³ = 98

Explanation:

Given x-y=2 ---(1)

xy = 15 ----(2)

____________________________

We know the algebraic identity:

a³-b³ = (a-b)³+3ab(a+b)

____________________________

x³-y³

= (x-y)³ +3xy(x-y)

= 2³ + 3×15×2 [ from (1)&(2)]

= 8+90

= 98

Therefore,

x³-y³ = 98

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