Question

[Nguyễn Thị Mai Trang]

A=-2/9+(-3)/4+3/5+1/15+1/57+1/3-1/36

Answer 1

[Emma]

$A=\frac{-2}{9}+\frac{-3}{4}+\frac{3}{5}+\frac{1}{15}+\frac{1}{57}+\frac{1}{3}-\frac{1}{36}$

$\to A=(\frac{-2}{9}+\frac{-3}{4}+\frac{1}{3}-\frac{1}{36})+(\frac{3}{5}+\frac{1}{15})+\frac{1}{57}$

$\to A=(\frac{-8}{36}+\frac{-27}{36}+\frac{12}{36}-\frac{1}{36})+(\frac{9}{15}+\frac{1}{15})+\frac{1}{57}$

$\to A=\frac{-2}{3}+\frac{2}{3}+\frac{1}{57}$

$\to A=0+\frac{1}{57}$

$\to A=\frac{1}{57}$

Vậy $A=\frac{1}{57}$

Answer 2

[ღᏠᎮღ🆃🆄ấ🅽ঔ 🅽🅰🅼ঌ❄๖ۣۜ]

Gọi $ƯCLN(12n+1,30n+2)=d(d>0,d\in Z)$

$\Rightarrow 12n+1⋮d,30n+2⋮d$

$\Rightarrow 60n+5⋮d,60n+4⋮d$

$\Rightarrow 60n+5-60n-4⋮d$

$\Rightarrow 1⋮d$

$\Rightarrow d\in Ư\left(1\right)=\{1,-1\}$

$\Rightarrow \frac{12n+1}{30n+2}$ là phân số tối giản với mọi số nguyên n