Question

bai 1: Tinh nhanh 

a) 1/2 + 1/4 + 1/8 + 1/16 + 1/32

b) 1/2 x 1/2 + 1/2 x 1/3 + 1/3 + 1/3 + 1/4 + 1/4 x 1/5 + 1/5 x 1/6

Answer 1

1.a 

1/2+1/4+1/8+1/16+1/32

= 1/2+1/2-1/4+1/4-1/8+1/8-1/16+1/16-1/32

= 1-1/32=31/32

Answer 2

1b

\(\frac{1}{2}.\frac{1}{2}+\frac{1}{2}.\frac{1}{3} +\frac{1}{3}+\frac{1}{3}+\frac{1}{4}+\frac{1}{4}.\frac{1}{5}+\frac{1}{5}.\frac{1}{6}\)

\(=\frac{1}{4}+\frac{1}{6}+\frac{2}{3}+\frac{1}{4}+\frac{1}{20}+\frac{1}{30}\)

\(=\frac{5}{20}+\frac{5}{30}+\frac{20}{30}+\frac{5}{20}+\frac{1}{20}+\frac{1}{30}\)

\(=\left(\frac{5}{20}+\frac{5}{20}+\frac{1}{20}\right)+\left(\frac{5}{30}+\frac{20}{30}+\frac{1}{30}\right)\)

\(=\frac{11}{20}+\frac{26}{30}\)

\(=\frac{11}{20}+\frac{13}{15}\)

\(=\frac{17}{12}\)

Answer 3

Đó là các cách bạn Võ Thạch Tín đã nêu ra nên mình ko còn câu trả lời nào hết