đặt a = $\sqrt{x+3}$ , b = $\sqrt{y+1}$
ta có: $\left \{ {{a+2b=3} \atop {2a+b=5}} \right.$
<=>$\left \{ {{2a+4b=6} \atop {2a+b=5}} \right.$
<=> $\left \{ {{2a+4b-2a-b=6-5} \atop {2a+b=5}} \right.$
<=>$\left \{ {{3b=1} \atop {2a+b=5}} \right.$
<=>$\left \{ {{b=1/3} \atop {a=7/3}} \right.$
=>$\left \{ {{\sqrt{x+3} =7/3 } \atop {\sqrt{y+1} =1/3 }} \right.$
<=>$\left \{ {{x+3=49/9} \atop {y+1=1/9}} \right.$
<=>$\left \{ {{x=22/9} \atop {y=-8/9}} \right.$
