Expanding binomials raised to the second power is easy, but going beyond is much harder. Thankfully, pascal's triangle has our back.
The graphic above (credit: Wikipedia) shows how the triangle is formed. Once you can create this triangle, you need to know how to apply it to expand the binomial. I used each of the rows in pascal's triangle above to find the solution to the first 4 powers of the binomial (x+3). Note that I start with x at the high power and drop one from the power from term to term while the 3 starts with a power of zero and I increment it up to 4 at the end.
A Practice worksheet I made for this quiz
For more information, try the wikipedia page on this.
For some practice try this worksheet.