Question

Expand ${(y-3)}^2$ using appropriate identity.

Answer 1

Using the identity is $(a-b{)}^2=a^2+b^2-2ab$.

Given: ${(y-3)}^2$ we apply the above identity by taking

$a=y$ and $b=-3$

We get, ${(y-3)}^2={\left(y\right)}^2+{\left(3\right)}^2-(2\times y\times 3)=y^2+9-6y$

Hence, ${(y-3)}^2=y^2-6y+9$.