3分之2加15分之2加35分之2加63分之2找规律计算
问题描述:
3分之2加15分之2加35分之2加63分之2找规律计算
答
2/3+2/15+2/35+2/63
=2/1×3+2/3×5+2/5×7+2/7×9
=2×﹙1/3+1/3×1/5+1/5×1/7+1/7×1/9﹚
=2×﹙2/5+1/5×1/7+1/7×1/9﹚
=2×﹙3/7+1/7×1/9﹚
=2×4/9
=8/9