https://www.google.com/search?q=the+binomial+theorem&espv=2&biw=656&bih=639&source=lnms&tbm=isch&sa=X&sqi=2&pjf=1&ved=0ahUKEwi-r526xt3KAhVX8WMKHfhaDZEQ_AUIBygC#imgrc=QFJv_8kBHdr6dM%3A