1.

If x-y=2 and xy=15 find the x^3-y^3​

Answer»

Answer:

116 or 56

Step-by-step explanation:

x-y =2

or

x= y+2

substitute this in XY = 15

(y+2)y =15

y^2 + 2Y = 15

y^2 + 2y - 15 = 0

solving quadratic eqn

y^2 - 3Y + 5y -15 = 0

y = -5 y = 3

x - y = 2

when y = 3 ,x = 5

when y= 2, x = 4

so x^3 - y^3 = 5^3 - 3^3 = 125 - 9 = 116

or

4^3 - 2^3 = 64 - 8 = 56

so ans is 116 or 56


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