Mike often argues ______ his friend ______ small things, which makes all of us very unhappy. A. with; for B. to; for C. to; about D. with; about 答案:D观察下列等式:11×2=1-12,12×3=12-13,13×4=13-14,将以上三个等式两边分别相加得:11×2+12×3+13×4=1-12+12-13+13-14(1)猜想并写出:1n(n+1)=1n-1n+11n-1n+1. 11×2+12×3+…+12013×2014=2013201420132014;(2)探究并计算:12×4+14×6+16×8+…+12012×2014.