A= 2.(\(\frac{4}{1.5}\)+\(\frac{4}{5.9}\)+...................+\(\frac{4}{49.53}\))

A=2.(\(\frac{4}{1}\)- \(\frac{4}{5}\)+\(\frac{4}{5}\)-\(\frac{4}{9}\)............... +\(\frac{4}{49}\)-\(\frac{4}{53}\))

A=2.(\(\frac{4}{1}\)-\(\frac{4}{53}\))

A=2.\(\frac{208}{53}\)

A=\(\frac{416}{53}\)                    

a. Miêu tả

b. So sánh

c. Hình ảnh cao lớn, vĩ đại của Bác trong lòng anh đội viên

a)Vi \(\widehat{xOy}\)va \(\widehat{yOt}\)la 2 goc ke bu nen =>

\(\widehat{xOy}\)+ \(\widehat{yOt}\)= \(\widehat{xOt}\)

120+\(\widehat{yOt}\)=180

\(\widehat{yOt}\)=60

b)Vi Om la tia phan giac cua  Ox va Oy nen => \(\widehat{xOm}\)=\(\widehat{mOy}\)=\(\frac{\widehat{xOy}}{2}\)=\(\frac{120}{2}\)=60

Vi \(\widehat{xOm}\)<\(\widehat{xOt}\)(60<180)nen => Om nam giua Ox va Ot

=>\(\widehat{xOm}\)+ \(\widehat{mOt}\)=\(\widehat{xOt}\)

60+\(\widehat{mOt}\)=180

\(\widehat{mOt}\)= 120

c) Vi On la tia phan giac cua Oy va Ot nen =>\(\widehat{yOn}\)= \(\widehat{nOt}\)=\(\frac{\widehat{yOt}}{2}\)=\(\frac{60}{2}\)=30

Vi Om nam giua Ox va Oy

      On nam giua Oy va Ot

      Oy nam giua Ox va Ot

=> Oy nam giua Om va On

=>\(\widehat{mOy}\)+ \(\widehat{yOn}\)=\(\widehat{mOn}\)

 60 +30 =\(\widehat{mOn}\)

\(\widehat{mOn}\)=90

BAI 2

=\(\frac{1}{2}\).\(\frac{2}{3}\)............\(\frac{19}{20}\)

=\(\frac{1.2.3.4........19}{2.3.4..........20}\)

=\(\frac{1}{20}\)