\(27^{11}=\left(3^3\right)^{11}=3^{3.11}=3^{33};81^8=\left(3^4\right)^8=3^{4.8}=3^{32}\\ Vì:3^{33}>3^{32}.Nên:27^{11}>81^8\)

\(5x\left(x-3\right)-3\left(x+1\right)=-12\)

\(5x\left(x-3\right)-3\left(x+1\right)+12=0\)

\(5x\left(x-3\right)-3\left(x+1-4\right)=0\)

\(5x\left(x-3\right)-3\left(x-3\right)=0\)

\(\left(5x-3\right)\left(x-3\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}5x-3=0\\x-3=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{3}{5}\notin Z\left(loại\right)\\x=3\end{matrix}\right.\)

cô ơi em xin lỗi 

x là dấu nhân ạ

Cái này của em còn thiếu phân số \(\dfrac{1}{15}\)

Với công thức: (gọi số điểm phân biệt là n) số đường thẳng: n.(n-1):2 (đây là khi không có 3 điểm thẳng hàng), sẽ có:

5.(5-1):2=5.4:2=20:2=10 đường thẳng

1-3+5-7+9-11+.......+2021-2023

=(1-3)+(5-7)+(9-11)+...+(2021-2023)

=(-2)+(-2)+(-2)+....+(-2) (có 506 số -2)

=506 x (-2)

=-1012

cảm ơn bạn nhé

\(\dfrac{x}{-2}=-\dfrac{8}{x}\left(x\ne0\right)\\ =>x.x=\left(-2\right).\left(-8\right)\\ =>x^2=16\\ =>x=\pm4\)

\(\dfrac{x}{-2}=\dfrac{-8}{x}\\ x.x=\left(-8\right).\left(-2\right)=16=4.4=\left(-4\right).\left(-4\right)\\ Vậy:\left[{}\begin{matrix}x=4\\x=-4\end{matrix}\right.\)

Vì : 4/5 > 6/11 > 5/9 nên trong 3 ngày ngày thứ nhất bán vải màu hồng là được nhiều nhất

Thầy ơi, vải tím là \(\dfrac{7}{11}\) chứ không phải \(\dfrac{6}{11}\) nhé thầy.

\(a,MSC:360\\ -\dfrac{3}{8}=\dfrac{-3.45}{8.45}=\dfrac{-135}{360};\dfrac{11}{24}=\dfrac{11.15}{24.15}=\dfrac{165}{360};\dfrac{11}{18}=\dfrac{11.20}{18.20}=\dfrac{220}{360}\\ ;\dfrac{-7}{9}=\dfrac{-7.40}{9.40}=\dfrac{-280}{360};\dfrac{4}{5}=\dfrac{4.72}{5.72}=\dfrac{288}{360}\\ b,MSC:135\\ \dfrac{-4}{15}=\dfrac{-4.9}{15.9}=\dfrac{-36}{135};\dfrac{7}{9}=\dfrac{7.15}{9.15}=\dfrac{105}{135};\dfrac{-1}{3}=\dfrac{-1.45}{3.45}=\dfrac{-45}{135}\\ ;\dfrac{2}{5}=\dfrac{2.27}{5.27}=\dfrac{54}{135};0=\dfrac{0}{135};\dfrac{13}{45}=\dfrac{13.3}{45.3}=\dfrac{39}{135}\)

\(a,\dfrac{2}{3}< \dfrac{x}{12}< \dfrac{7}{6}\\ \dfrac{2.4}{3.4}< \dfrac{x}{12}< \dfrac{7.2}{6.2}\\ \dfrac{8}{12}< \dfrac{x}{12}< \dfrac{14}{12}\\ Vậy:x\in\left\{9;10;11;12;13\right\}\\ PS:\left\{\dfrac{9}{12};\dfrac{10}{12};\dfrac{11}{12};\dfrac{12}{12};\dfrac{13}{12}\right\}\)

\(b,\dfrac{25}{9}< \dfrac{50}{x}< \dfrac{10}{3}\\ \dfrac{25.2}{9.2}< \dfrac{50}{x}< \dfrac{10.5}{3.5}\\ \dfrac{50}{18}< \dfrac{50}{x}< \dfrac{50}{15}\\ Nên:x\in\left\{17;16\right\}\\ Vậy:PS\left\{\dfrac{50}{17};\dfrac{50}{16}\right\}\)

a; 8 = 2³; 24 = 2³.3; 18 = 2.3²; 5 = 5

 BCNN(8; 24; 18; 5) = 2³.3².5 = 360

\(\dfrac{-3}{8}\) = \(\dfrac{-3.45}{8.45}\) = \(\dfrac{-135}{360}\);  \(\dfrac{11}{24}\) =  \(\dfrac{11.15}{24.15}\) = \(\dfrac{165}{360}\) 

\(\dfrac{11}{18}\) = \(\dfrac{11.20}{18.20}\) = \(\dfrac{220}{360}\); \(\dfrac{-7}{9}\) = \(\dfrac{-7.40}{9.40}\) = \(\dfrac{-280}{360}\)

 \(\dfrac{4}{5}\) = \(\dfrac{4.72}{5.72}\) = \(\dfrac{288}{360}\); 

\(\dfrac{-7}{9}\); \(\dfrac{-3}{8}\); \(\dfrac{11}{24}\); \(\dfrac{11}{18}\); \(\dfrac{4}{5}\)

b; 15 = 3.5; 9 = 3²; 3 = 3; 45 = 3².5

BCNN(15; 9; 45) = 3².5

\(\dfrac{-4}{15}\) = \(\dfrac{-4.3}{15.3}\) = \(\dfrac{-12}{45}\); \(\dfrac{7}{9}\) = \(\dfrac{7.5}{9.5}\) = \(\dfrac{35}{45}\); \(\dfrac{-1}{3}\) = \(\dfrac{-1.15}{3.15}\) = \(\dfrac{-15}{45}\)

\(\dfrac{2}{5}\) = \(\dfrac{2.9}{5.9}\) =  \(\dfrac{18}{45}\); 0 = \(\dfrac{0}{45}\); \(\dfrac{13}{45}\)

\(\dfrac{-1}{3}\); \(\dfrac{-4}{15}\); 0; \(\dfrac{13}{45}\); \(\dfrac{2}{5}\);  \(\dfrac{7}{9}\)