文档介绍：学生姓名孔子悦年级小六授课时间2013年5月16日教师姓名杨勇飞课时2课题复习简便计算教学目标掌握简便运算的方法重点掌握简便运算的方法难点掌握简便运算的方法×+×+×1/(1×2×3×4)+1/(2×3×4×5)+1/(3×4×5×6)+...+1/(7×8×9×10)=(1/3)×[1/(1×2×3)-1/(2×3×4)]+(1/3)×[1/(2×3×4)-1/(3×4×5)]+(1/3)×[1/(3×4×5)-1/(4×5×6)]+...+(1/3)×[1/(7×8×9)-1/(8×9×10)]=(1/3)×[1/(1×2×3)-1/(2×3×4)+1/(2×3×4)-1/(3×4×5)+1/(3×4×5)-1/(4×5×6)+...+1/(7×8×9)-1/(8×9×10)]=(1/3)×[1/(1×2×3)-1/(8×9×10)]=(1/3)×[(1/6)-(1/720)]=(1/3)×(119/720)=119/2160仅供参考:(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/+1/5+1/6)-(1+1/2+1/3+1/4+1/5+1/6)*(1/2+1/3+1/4+1/5)设1+1/2+1/3+1/4+1/5=a1/2+1/3+1/4+1/5=b(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/4+1/5+1/6)-(1+1/2+1/3+1/4+1/5+1/6)*(1/2+1/3+1/4+1/5)=a*(b+1/6)-(a+1/6)*b=1/6(a-b)=1/6 4/3-7/12+9/20-11/30+13/42-15/56=(1+1/3)-(1/3+1/4)+(1/4-1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)=1-1/8=7/81+3+5+7+9+11............+199=(1+199)*100/2=200*100/2=10000(1x2x3+3x6x9+7x14x21)/(1x3x5+3x9x15+7x21x35)=3(1×2+6×9+7×14×7)/3(1×5+9×15+7×7×35)=(1×2+6×9+7×14×7)/(1×5+9×15+7×7×35)=14(4+7×7)/5(1+3×9+7×7×7)=14×53/5×7(4+7×7)=14×53/35×53=14/35