Ta có:
B=36/1.3.5+36/3.5.7+36/5.7.9+.......+36/25.27.29
B=9.(4/1.3.5+4/3.5.7+4/5.7.9+...+4/25.27.29)
B=9.(1/1.3-1/3.5+1/3.5-1/5.7+...+1/25.27-1/27.29)
B=9.(1/3-1/27.29)
B=3-1/87
B=261/87-1/87
B=260/87
CHO MÌNH 5 SAO VÀ CÂU TRẢ LỜI HAY NHẤT NHÉ!!!!!!!!!!!