Answer
$r^{2}-2rs+s^{2}$
Work Step by Step
Step 1: $(r-s)^{2}$
Step 2: Using the special product, $(r-s)^{2}=(r)^{2}-2(r)(s)+(s)^{2}$
Step 3: $(r)^{2}-2(r)(s)+(s)^{2}=r^{2}-2rs+s^{2}$
Step 4: Therefore, the required answer is $r^{2}-2rs+s^{2}$