radius of the circle

Question

alones · Answer

$ \color{brown}{x^2+y^2=15} $

anonymous · Answer

what are you looking for?

s4sensitiveandshy · Answer

$$(x-h)^2+(y-k)^2=r^2$$ equation of a circle
 where (h,k) is the center and r = radius

alones · Answer

Well, umm I’m not sure neither, tho here are the choices :3
	3
  $$  \sqrt{15   } $$
  $$  \sqrt{11  } $$

johnweldon1993 · Answer

Read @S4Sensitiveandshy post above :)

johnweldon1993 · Answer

$\large x^2 + y^2 = 15$ <--your equation
$\large (x - h)^2 + (y - k)^2 = r^2$ <--equation of a circle

Comparing the 2..since we know 'r' is the radius of the circle

$$\large r^2 = 15$$

What would 'r' be?

s4sensitiveandshy · Answer

there is 15 which is r^2 how would you get r ??

alones · Answer

I don’t know, I barely understand this lesson

s4sensitiveandshy · Answer

here is an example  $$y^2  = \sqrt{y^2} $$ to cancel ou the square you should take square root 
because sqrt{y} can be written as $$(y^2)^\frac{ 1 }{ 2 }$$
2 would cancel each other out left with y^2 which is same as y

s4sensitiveandshy · Answer

so take square root both sides.

alones · Answer

Uhh how would i do that, sorry i still dont' understand x3

s4sensitiveandshy · Answer

$$y^2=4$$
take square root ( the radical sign both sides)
$$\sqrt{y^2}= \sqrt{4}$$
square root and square will cancel each other out  
and the square root of 4 is 2 $$y=  2$$

s4sensitiveandshy · Answer

just like that. 
 $$r^2=15$$ take square root

sweetburger · Answer

remember that r is the radius of the circle
$$\sqrt{r^2} = \sqrt{15}, r = \sqrt{15}$$

s4sensitiveandshy · Answer

thank you.

rhondasommer · Answer

well $$√{r^2}$$ the square root and the 2 (it is squaring the radius) cancels out. just so you know the reasoning behind what sean said