Answer:
hi,
Step-by-step explanation:
Let say P=(x,y) a point of the locus
[tex]Distance\ from\ P\ to\ (2,1)= \sqrt{(x-2)^2+(y-1)^2} \\Distance\ from\ P\ to\ (1,2)= \sqrt{(x-1)^2+(y-2)^2} \\\\\sqrt{(x-2)^2+(y-1)^2} =2*\sqrt{(x-1)^2+(y-2)^2} \\\\(x-2)^2+(y-1)^2=4*((x-1)^2+(y-2)^2)\\\\3x^2-4x+3y^2-14y+15=0\\\\[/tex]
[tex]3x^2-4x+3y^2-14y+15=0\\3(x^2-2*\dfrac{2}{3} x)+3(y^2-2*\dfrac{7}{3}*y) +15=0\\3(x^2-2*\dfrac{2}{3}*x+\dfrac{4}{9})+3(y^2-2*\dfrac{7}{3}*y+\dfrac{49}{9} ) +15-\dfrac{4}{3}-\dfrac{49}{3}=0\\\\3(x-\dfrac{2}{3})^2+3(y-\dfrac{7}{3})^2-\dfrac{8}{3}=0\\\\\\\boxed{(x-\dfrac{2}{3})^2+(y-\dfrac{7}{3})^2=\dfrac{8}{9}}\\\\[/tex]
Locus is the circle of center (2/3,7/3) and radius =2√2 /3.
