mik chưa học đến bài đó nhưng chúc b mai thi tốt nhé!
\(a,ĐK:x\ne0;x\ne5\\ B=\dfrac{x^2-25+2x^2-12x-x^2+8x+25}{2x\left(x-5\right)}=\dfrac{2x\left(x-2\right)}{2x\left(x-5\right)}=\dfrac{x-2}{x-5}\\ b,x=3\Leftrightarrow A=\dfrac{3+6}{5-3}=\dfrac{9}{2}\\ c,\text{Câu a}\\ d,E=B-A=\dfrac{x-2}{x-5}+\dfrac{x+6}{x-5}=\dfrac{2x+4}{x-5}=\dfrac{2\left(x-5\right)+14}{x-5}=2+\dfrac{14}{x-5}\in Z\\ \Leftrightarrow x-5\inƯ\left(14\right)=\left\{-14;-7;-2;-1;1;2;7;14\right\}\\ \Leftrightarrow x\in\left\{-9;-2;3;4;6;7;12;19\right\}\)