according to ques,

concentric circles with centre \[\left( 1,\text{ }2 \right)\] and with radius ‘r’ can be written as,

^{\[{{\left( x\text{ }\text{ }1 \right)}^{2}}~+\text{ }{{\left( y\text{ }\text{ }2 \right)}^{2}}~=\text{ }{{r}^{2}}\]}

Differentiating with respect to x,

We have,