Question

Answer 1

a: Thay x=5 vào A, ta được:

\(A=\dfrac{5+1}{5+3}=\dfrac{6}{8}=\dfrac{3}{4}\)

Answer 2

\(a,A=\dfrac{5+1}{5+3}=\dfrac{6}{8}=\dfrac{3}{4}\\ b,B=\dfrac{3x+9+6x+x^2-3x}{\left(x-3\right)\left(x+3\right)}=\dfrac{\left(x+3\right)^2}{\left(x-3\right)\left(x+3\right)}=\dfrac{x+3}{x-3}\\ c,P=AB=\dfrac{x+1}{x+3}\cdot\dfrac{x+3}{x-3}=\dfrac{x-3+4}{x-3}=1+\dfrac{4}{x-3}\in Z\\ \Leftrightarrow x-3\inƯ\left(4\right)=\left\{-4;-2;-1;1;2;4\right\}\\ \Leftrightarrow x\in\left\{-1;1;2;4;5;7\right\}\left(tm\right)\)