Which of the following is the equation of a circle whose center is at the origin and whose radius is 4?
a. x2 + y2 = 2
b. x2 + y2 = 4
c. x2 + y2 = 16

C. x^2 + y^2 = 16

Step-by-step explanation

The standard form:  (x - h)^2  +  (y-k)^2   =   r^2, where (h, k) is the center and r is the radius of the circle.

Given: (h, k) = (0, 0) and r = 4.

Now plug in the given values in the standard form, we get

(x - 0)^2 + (y - 0)^2 = 4^2

x^2 + y^2 = 16

The answer is C. x^2 + y^2 = 16

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1696 hundred thousand

step-by-step explanation:

{x = -1/2 ,   y = -1

step-by-step explanation:

solve the following system:

{2 x + y = -2

{10 x - 3 y = -2

in the first equation, look to solve for y:

{2 x + y = -2

{10 x - 3 y = -2

subtract 2 x from both sides:

{y = -2 x - 2

{10 x - 3 y = -2

substitute y = -2 x - 2 into the second equation:

{y = -2 x - 2

{10 x - 3 (-2 x - 2) = -2

10 x - 3 (-2 x - 2) = (6 x + 6) + 10 x = 16 x + 6:

{y = -2 x - 2

{16 x + 6 = -2

in the second equation, look to solve for x:

{y = -2 x - 2

{16 x + 6 = -2

subtract 6 from both sides:

{y = -2 x - 2

{16 x = -8

divide both sides by 16:

{y = -2 x - 2

{x = -1/2

substitute x = -1/2 into the first equation:

{y = -1

{x = -1/2

collect results in alphabetical order:

answer:   {x = -1/2 ,   y = -1