Đáp án:(a;b)= (0;8); (-1;2); ($\frac{1}{3};6$); (-1;4)
Giải thích các bước giải:
(ab+1)(b-5)=3
⇒ab+1; b-5∈UC(3)={-1;1;-3;3}
⇒(1)$\left \{ {{ab+1=1} \atop {b-5=3}} \right.$⇔ $\left \{ {{a=0} \atop {b=8}} \right.$
⇒(2)$\left \{ {{ab+1=-1} \atop {b-5=-3}} \right.$⇔ $\left \{ {{a=-1} \atop {b=2}} \right.$
⇒(3)$\left \{ {{ab+1=3} \atop {b-5=1}} \right.$⇔ $\left \{ {{a=\frac{1}{3}} \atop {b=6}} \right.$
⇒(4)$\left \{ {{ab+1=-3} \atop {b-5=-1}} \right.$⇔ $\left \{ {{a=-1} \atop {b=4}} \right.$
⇒(a;b)= (0;8); (-1;2); ($\frac{1}{3};6$); (-1;4)
