Answer
$y^{2}-\dfrac{4}{7}y+\dfrac{4}{49}$
Work Step by Step
$\Big(y-\dfrac{2}{7}\Big)^{2}$
Apply the formula for squaring a binomial, which is $(a-b)^{2}=a^{2}-2ab+b^{2}$.
Here, $a=y$ and $b=\dfrac{2}{7}$
$\Big(y-\dfrac{2}{7}\Big)^{2}=y^{2}-2(y)\Big(\dfrac{2}{7}\Big)+\Big(\dfrac{2}{7}\Big)^{2}=y^{2}-\dfrac{4}{7}y+\dfrac{4}{49}$
