\(n^2+3⋮n+1\)

\(\Rightarrow n^2+3-n\left(n+1\right)⋮n+1\)

\(\Rightarrow n^2+3-n^2-n⋮n+1\)

\(\Rightarrow3-n⋮n+1\)

\(\Rightarrow3-n+n+1⋮n+1\)

\(\Rightarrow4⋮n+1\)

\(\Rightarrow n+1\in U\left(4\right)=\left\{-1;1;-2;2;-4;4\right\}\left(n\inℕ\right)\)

\(\Rightarrow n\in\left\{-2;0;-3;1;-5;3\right\}\)

\(\dfrac{3}{1\times4}x+\dfrac{3}{4\times7}x+\dfrac{3}{7\times10}x+...+\dfrac{3}{31\times34}x=33\)

\(x\left(\dfrac{3}{1\times4}+\dfrac{3}{4\times7}+\dfrac{3}{7\times10}+...+\dfrac{3}{31\times34}\right)=33\)

\(x\left(\dfrac{1}{1}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{31}-\dfrac{1}{34}\right)=33\)

\(x\left(1-\dfrac{1}{34}\right)=33\)

\(\dfrac{33}{34}x=33\)

\(x=34\)

\(\dfrac{3}{1.4}x+\dfrac{3}{4.7}x+\dfrac{3}{7.10}x+...+\dfrac{3}{31.34}x=33\)

\(x.3\left(\dfrac{1}{1.4}+\dfrac{1}{4.7}+\dfrac{1}{7.10}+...+\dfrac{1}{31.34}\right)=33\)

\(x.3.\dfrac{1}{3}\left(1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{31}-\dfrac{1}{34}\right)=33\)

\(x.\left(1-\dfrac{1}{34}\right)=33\)

\(x.\dfrac{33}{34}=33\)

\(x=33:\dfrac{33}{34}=33.\dfrac{34}{33}\)

\(x=34\)

Bài này thiếu dữ kiện

\(x-\left[3+\left(2^4.3-48:6-3\right)\right]=10\)

\(x-\left[3+\left(16.3-8-3\right)\right]=10\)

\(x-\left[3+48-8-3\right]=10\)

\(x-40=10\)

\(x=50\)

\(x-\left[3+\left(2^4.3-48:6-3\right)\right]=10\)

\(x-\left[3+\left(16.3-48:6-3\right)\right]=10\)

\(x-\left[3+48-8-3\right]=10\)

\(x-46=10\)

\(x=10+46\)

\(x=56\)

\(x-\left[3+\left(2^4.3-48:6-3\right)\right]=10\)

\(x-\left[3+\left(48-8-3\right)\right]=10\)

\(x-\left[3+37\right]=10\)

\(x-40=10\)

\(x=10+40\)

\(x=50\)

1 tới 9: 9 chữ số.

10-99: \(2\cdot\left(99-10+1\right)=180\) chữ số.

100-480: \(3\cdot\left(480-100+1\right)=1143\) chữ số.

Tổng: \(9+180+1143=1332\) chữ số.

1332 chữ số nha bạn

Hiệu vận tốc của ô tô và xe máy là :

\(40-25=15\left(km/h\right)\)

Thời gian 2 xe gặp nhau sau :

\(15:15=1\left(giờ\right)\)

Đáp số...

ai cứu tui với 

\(0,4\%hay40\%?\)

helppppp meeeeeeeeee

 Ta có: 12 hs tương ứng với 4%

Số học sinh trường đó có là:

     \(12:4\%=300\) ( hs )

     Đ/S:...