Question

1/2 + 1/6 + 1/12 + 1/20 = ??

tính bằng cách thuận tiện ( mn nói từng bước giải nhé :> )

Answer 1

\(=\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}\right)+\dfrac{1}{20}=\left(\dfrac{6}{12}+\dfrac{2}{12}+\dfrac{1}{12}\right)+\dfrac{1}{20}=\dfrac{3}{4}+\dfrac{1}{20}=\dfrac{15}{20}+\dfrac{1}{20}=\dfrac{16}{20}=\dfrac{4}{5}\)

Answer 2

=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5

=1-1/5

=4/5