Question

Tính nhanh :

a) \(\frac{2015\cdot2017-1}{2014+2015\cdot2016}\)

b) \(\frac{1}{1\cdot5}+\frac{1}{5\cdot9}+...+\frac{1}{2011\cdot2015}\)

c)\(\frac{12}{35}+\frac{1212}{3535}+\frac{121212}{353535}+\frac{12121212}{35353535}\)

Answer 1

a,\(\frac{2015.2016+2015-1}{2014+2015.2016}=\frac{2015.2016+2014}{2014+2015.2016}=1\)\(1\)

b,\(=1-\frac{1}{5}+\frac{1}{5}...-\frac{1}{2011}+\frac{1}{2011}-\frac{1}{2015}=1-\frac{1}{2015}=\frac{2014}{2015}\)

c,\(=\frac{12}{35}+\frac{12}{35}+\frac{12}{35}+\frac{12}{35}=\frac{12}{35}.4=\frac{48}{35}\)

Answer 2

48/35 nha

Answer 3

b>=1-1/5+1/5-1/9+...+1/2011-1/2015

 =1-1/2015

=2014/2015

c>=12/35+12/35+12/35+12/35

=12/35x4

=48/35