Complete the square to rewrite the following equation. Identify the center and radius of the circle. You must show all work and calculations to receive credit.

x2 − 4x + y2 + 8y = −4

Question

Complete the square to rewrite the following equation. Identify the center and radius of the circle. You must show all work and calculations to receive credit.

x2 − 4x + y2 + 8y = −4

snowflake0531 · Answer

$$(x^2-4x) + (y^2+8y) = -4$$ ignore the right half for now
and spilt the left to x^2 -4x and y^2 + 8y
let's first look at 
$$x^2-4x$$
What can we add to this to make this a perfect square?

snowflake0531 · Answer

x^2-4x + __ = (x-_)^2

kekeman · Answer

So when we are finding the y^2 value  we have to find b from 2ab in each term?

York · Answer

Complete the square method: for x and y, u wanna get that third piece because you have x^2 and x^1 so you want x^0, a value with no x; to get this you take the value with the x on it, and divide by two, then square; x^2-4x+4, then you have to add that 4 to the other side too, and do the same for y

kekeman · Answer

Mmmm ok

kekeman · Answer

So the center would be (2, -4) and the radius would be 4? right

kekeman · Answer

Idk no more tbh

snowflake0531 · Answer

@kekeman wrote:

So the center would be (2, -4) and the radius would be 4? right

Yes

York · Answer

yeah

dgreer2 · Answer

@snowflake and @york  Nice job!