# How do you write the equation of the circle with radius 4 and center at (0, 0)?

Nov 24, 2016

${x}^{2} + {y}^{2} = 16$

#### Explanation:

standard eqn. of circle with centre$\text{ "(a,b)," }$ radius $\text{ } r$

${\left(x - a\right)}^{2} + {\left(y - b\right)}^{2} = {r}^{2}$

In this case

$r = 4 , \text{ } \left(a , b\right) = \left(0 , 0\right)$

we have

${\left(x - 0\right)}^{2} + {\left(y - 0\right)}^{2} = {4}^{2}$

giving

${x}^{2} + {y}^{2} = 16$