Question

What is $(x-y{)}^3$?

• A. $x^3-y^3+3xy(x-y)$
• B. $x^3+y^3-3xy(x+y)$
• C. $x^3-y^3-3xy(x-y)$
• D. $x^3+y^3+3xy(x+y)$

Answer 1

The correct option is C

$x^3-y^3-3xy(x-y)$

We have the identity:

$(a-b{)}^3=a^3-b^3-3ab(a-b)$

By replacing $a$ by $x$ and $b$ by $y$, we get

$(x-y{)}^3=x^3-y^3-3xy(x-y)$