dùng kí hiệu góc đi chị 

\(-\dfrac{13}{12}-\dfrac{17}{17}\\ =-\dfrac{13}{12}-1\\ =-\dfrac{13}{12}-\dfrac{12}{12}\\ =-\dfrac{13}{12}+\left(-\dfrac{12}{12}\right)\\ =-\dfrac{25}{12}\)

\(\left|3x-\dfrac{3}{5}\right|-0,2=\dfrac{1}{4}\\ \Leftrightarrow\left|3x-\dfrac{3}{5}\right|-\dfrac{1}{5}=\dfrac{1}{4}\\ \Leftrightarrow\left|3x-\dfrac{3}{5}\right|=\dfrac{9}{20}\\ \Leftrightarrow\left[{}\begin{matrix}3x-\dfrac{3}{5}=\dfrac{9}{20}\\3x-\dfrac{3}{5}=-\dfrac{9}{20}\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{7}{20}\\x=\dfrac{1}{20}\end{matrix}\right.\)

:)) m chữa bệnh đi khịa người cho t đi 

\(a)\\ P=\dfrac{x+2}{x+3}-\dfrac{5}{x^2+x-6}+\dfrac{1}{2-x}\\=\dfrac{x+2}{x+3}-\dfrac{5}{\left(x+3\right)\left(x-2\right)}-\dfrac{1}{x-2}\\ =\dfrac{\left(x+2\right)\left(x-2\right)}{\left(x+3\right)\left(x-2\right)}-\dfrac{5}{\left(x+3\right)\left(x-2\right)}-\dfrac{x+3}{\left(x+3\right)\left(x-2\right)}\\ =\dfrac{x^2-4-5-x-3}{\left(x+3\right)\left(x-2\right)}\\ =\dfrac{x^2-x-12}{\left(x+3\right)\left(x-2\right)}\\ =\dfrac{x^2-4x+3x-12}{\left(x+3\right)\left(x-2\right)}\\ =\dfrac{\left(x-4\right)\left(x+3\right)}{\left(x+3\right)\left(x-2\right)}=\dfrac{x-4}{x-2} \)

\(b)P=-\dfrac{3}{2}\\ \rightarrow\dfrac{x-4}{x-2}=-\dfrac{3}{2}\\ \Leftrightarrow2\left(x-4\right)=-3\left(x-2\right)\\\Leftrightarrow4x-16+3x-6=0\\ \Leftrightarrow7x-22=0\\ \Leftrightarrow x=\dfrac{22}{7} \)

tuk mà hổng lmj đc :((