Question

[Dung Hòa]

Tính nhanh:

\(\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}+\dfrac{1}{128}\)

c.7m²8dm²=.....m²

Answer 1

[ILoveMath]

\(\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}+\dfrac{1}{128}\\ =\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{16}+...+\dfrac{1}{64}-\dfrac{1}{128}\\ =\dfrac{1}{2}-\dfrac{1}{128}\\ =\dfrac{63}{128}\)

\(7m^28dm^2=7,08m^2\)

Answer 2

[Nguyễn Lê Phước Thịnh]

c: =7,08