${\left(x-5\right)}^2+{\left(y+5\right)}^2=9$  

$S=\left(5,-5\right),r=3$  

 

a) Rysunek pomocniczy:  

$S_1=\left(5,-2+4\right),r=4$  

$S_1=\left(5,2\right),r=4$  

${\left(x-5\right)}^2+{\left(y-2\right)}^2=16$  

 

$S_2=\left(8+4,-5\right),r=4$  

$S_2=\left(12,-5\right),r=4$  

${\left(x-12\right)}^2+{\left(y+5\right)}^2=16$  

 

$S_3=\left(5,-8-4\right),r=4$  

$S_3=\left(5,-12\right),r=4$  

${\left(x-5\right)}^2+{\left(y+12\right)}^2=16$  

 

$S_4=\left(2-4,-5\right),r=4$  

$S_4=\left(-2,-5\right),r=4$  

${\left(x+2\right)}^2+{\left(y+5\right)}^2=16$  

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b) Rysunek pomocniczy:

Korzystając z tw. Pitagorasa otrzymujemy:

$r^2+r^2=7^2$  

$2r^2=49\mid :2$  

$r^2=\frac{49}{2}$  

$r=\frac{7}{\sqrt{2}}$  

$r=\frac{7\sqrt{2}}{2}$