Question

Tính nhanh
3/4 + 3/28 + 3/70 + 3/130

Answer 1

12/13

Answer 2

=3/1.4  + 3/4.7 + 3/7.10 + 3/13.10

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

=8+4/13

=12/13

Answer 3

= \(\dfrac{3}{1.4}+\dfrac{3}{4.7}+\dfrac{3}{7.10}+\dfrac{3}{10.13}\) 

= \(1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{13}=1-\dfrac{1}{13}=\dfrac{12}{13}\)