k)

Did you know that squaring a binomial like is rooted in the distributive property? In this case, you can visualize it as multiplying by itself! When you do this, you apply the formula . Here, and , leading to an exciting expansion of !

When you simplify , you might be tempted to just multiply out, but pay attention! A common mistake is forgetting the negative sign or miscalculating the coefficients. Remember to carefully distribute each term, check your signs, and combine like terms properly. It’s a fun puzzle that requires a little patience!