1/52+49/52×51+49×48/52×51×50+.+49×...×1/52×...×3=?
问题描述：
1/52+49/52×51+49×48/52×51×50+.+49×...×1/52×...×3=?
1/52+49/52×51+49×48/52×51×50+.+49×...×1/52×...×=?
1/52+49/52×51+49×48/52×51×50+......+49×...×1/52×...×3=?
答
原式=51×50/52×51×50+50×49/52×51×50+49×48/52×51×50+48×47/52×51×50+.2×1/52×51×50=﹙51×50＋50×49＋49×48＋48×47＋.＋2×1﹚／52×51×50因为 1×2=1×2×3×1／3 2×3=1／3×﹙2×3×4-1×2×...