Question

tình nhanh 

\(\frac{3}{1x4}\)+ \(\frac{3}{4x7}\)+\(\frac{3}{7x10}\)+\(\frac{3}{10x13}\)

tính nhanh đó nha mấy bn 

tính nhanh phân số đó

ai nhanh mink tick

mink cần lắm rùi

Answer 1

=3/1-3/4+3/4-3/7+3/7-3/10+3/10-3/13

=1/1-1/4+1/4-1/7+1/7-1/10+1/10-1/13

=1-1/13

=12/13

Answer 2

3/1x4+3/4x7+3/7x10+3/10x13

=1-1/4+1/4-1/7+1/7-1/10+1/10-1/13

=1-1/13

=12/13

Answer 3

\(\frac{3}{1\times4}+\frac{3}{4\times7}+\frac{3}{7\times10}+\frac{3}{10\times13}\)

\(=3\times\left(\frac{1}{1\times4}+\frac{1}{4\times7}+\frac{1}{7\times10}+\frac{1}{10\times13}\right)\)

\(=3\times\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}\right)\)

\(=3\times\left(1-\frac{1}{13}\right)\)

\(=3\times\frac{12}{13}\)

\(=\frac{36}{13}\)

Answer 4

Thằng  Trần Hoàng Việt  lm sai rồi dơ mặt ban lãnh đạo CTV
\(\frac{3}{1.4}+\frac{3}{4.7}+...+\frac{3}{10.13}\)

\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+..+\frac{1}{10}-\frac{1}{13}\)

\(=1-\frac{1}{13}=\frac{12}{13}\)

Answer 5

\(\frac{3}{1\cdot4}+\frac{3}{4\cdot7}+\frac{4}{7\cdot10}+\frac{3}{10\cdot13}\)

\(=\frac{1}{1\cdot4}+\frac{1}{4\cdot7}+\frac{1}{7\cdot10}+\frac{1}{10\cdot13}\)

\(=\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}\)

\(=\frac{1}{1}-\frac{1}{13}\)

\(=\frac{13}{13}-\frac{1}{13}\)

\(=\frac{12}{13}\)