Question

Which of the following is the equation of the circle with center (4, 0) and r = sqrt 5?

x^2 + (y - 4)^2 = 5

x^2 + (y + 4)^2 = sqrt 5

(x + 4)^2 + y^2 = sqrt 5

(x - 4)^2 + y^2 = 5

Answer 1

the equation of a circle with center (h,k) and radius r is
\[ (x-h)^2 + (y-k)^2 = r^2 \]

Answer 2

\(\bf center \to ({\color{red}{ 4}},{\color{blue}{ 0}})\qquad radius=\sqrt{5}
\\ \quad \\
(x-{\color{red}{ h}})^2+(y-{\color{blue}{ k}})^2=r^2\)

Answer 3

replace h with 4, k with 0, and r with sqr(5)

Answer 4

notice that sqr(5)^2 is sqr(5)*sqr(5) = 5
so the answer must be either the first or last choice

Answer 5

Thank you!! Both of you. :0

Answer 6

yw