Question

. If x-y=3 Find the value of x3 - y3 - 9xy​

Answer 1

Answer:

$x^3-y^3-9xy=27$

Step-by-step explanation:

Given:-

$x-y=3$

To find:-

$x^3-y^3-9xy$

Solution:-

$x-y=3$ $($∵ $Given)$

$x=3+y$

By substituting $x$ value in $x^3-y^3-9xy$,

$=(3+y)^3-y^3-[9\times(3+y)\times y]$

⇒ $3^3+y^3+3(3)(y)(3+y)-y^3-9y(3+y)$ $[$∵ $(a+b)^3=a^3+b^3+3ab(a+b)]$

⇒ $27+y^3+9y(3+y)-y^3-9y(3+y)$

⇒ $27+y^3-y^3+9y(3+y)-9y(3+y)$

⇒ $27$

∴  $x^3-y^3-9xy=27$.