\(=3.\left(\frac{1}{2}+\frac{1}{6}+...+\frac{1}{9900}\right)\)
\(=3.\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{99.100}\right)\)
\(=3.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\right)\)
\(=3.\left(1-\frac{1}{100}\right)\)
\(=3.\frac{99}{100}=\frac{297}{100}\)
\(\frac{3}{2}+\frac{3}{6}+\frac{3}{12}+...+\frac{3}{9900}\\ =3\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}\right)\)
\(=3\left(\frac{2-1}{1.2}+\frac{3-2}{2.3}+...+\frac{100-99}{99.100}\right)\\ =3\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\right)\)
\(=3\left(1-\frac{1}{100}\right)=3.\frac{99}{100}=\frac{297}{100}\)
\(\frac{3}{2}+\frac{3}{6}+\frac{3}{12}+\frac{3}{20}+...+\frac{3}{9900}\)
\(=\frac{3}{1.2}+\frac{3}{2.3}+\frac{3}{3.4}+\frac{3}{4.5}+...+\frac{3}{99.100}\)
\(=3.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{99}-\frac{1}{100}\right)\)
\(=3.\left(1-\frac{1}{100}\right)\)
\(=3.\frac{99}{100}\)
\(=\frac{297}{100}\)
Bài làm
\(\frac{3}{2}+\frac{3}{6}+\frac{3}{12}+\frac{3}{20}+...+\frac{3}{9900}\)
\(=\frac{3}{1.2}+\frac{3}{2.3}+\frac{3}{3.4}+\frac{3}{4.5}+...+\frac{3}{99.100}\)
\(=3.\frac{1}{1.2}+3.\frac{1}{2.3}+3.\frac{1}{3.4}+3.\frac{1}{4.5}+...+3.\frac{1}{99.100}\)
\(=3.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{99.100}\right)\)
\(=3.\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{99}-\frac{1}{100}\right)\)
\(=3.\left(1-\frac{1}{100}\right)\)
\(=3.\left(\frac{100}{100}-\frac{1}{100}\right)\)
\(=3.\frac{99}{100}\)
\(=\frac{297}{100}\)
~ Sắp thi cuối học kì rồi, chúc cậu làm bài thật tốt để thi đỗ nhé, chỉ cần đủ điểm đỗ là được, không cần thừa quá nhiều đâu. ^^ ~
# Chúc_Bạn_Học_Tốt #
