$a)$  

$\{\begin{array}{l}{x}^2+y^2=4\\ x^2+y^2-4x=0\end{array}$  

$\{\begin{array}{l}{x}^2+y^2=4\\ x^2+y^2=4x\end{array}$  

$x^2+y^2=x^2+y^2$  

$4=4x$  

$x=1$  

$y^2=4-x^2=3$  

$y=\sqrt{3}\vee y=-\sqrt{3}$  

$\{\begin{array}{l}x=1\\ y=\sqrt{3}\end{array}\vee \{\begin{array}{l}x=1\\ y=-\sqrt{3}\end{array}$  

$A,B-\text{rozwiąznia układu roˊwnanˊ}$   

$A=\left(1;\sqrt{3}\right)$  

$B=\left(1;-\sqrt{3}\right)$    

 

$b)$  

$\{\begin{array}{l}{x}^2+y^2=1\\ x^2+{\left(y-4\right)}^2=9\end{array}$          

$\{\begin{array}{l}{x}^2=1-y^2\\ x^2+{\left(y-4\right)}^2=9\end{array}$           

$1-y^2+y^2-8y+16-9=0$  

$-8y=-8$  

$y=1$  

$x^2=1-y^2=0$  

$x=0$  

$\{\begin{array}{l}x=0\\ y=1\end{array}$  

$A=\left(0;1\right)$    

 

$c)$  

$\{\begin{array}{l}{x}^2-6x+y^2=0\\ x^2+2x+y^2=0\end{array}$    

$\{\begin{array}{l}{y}^2=6x-x^2\\ x^2+2x+y^2=0\end{array}$  

$x^2+2x+6x-x^2=0$  

$8x=0$  

$x=0$  

$y=6x-x^2=0$  

$\{\begin{array}{l}x=0\\ y=0\end{array}$  

$A=\left(0;0\right)$