Question

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Answer 1

Answers:

Equation is $(x+1)^2 + (y+2)^2 = 25$

Center is (-1, -2)

Radius = 5

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Work Shown:

$x^2+2x+y^2+4y=20\\\\(x^2+2x)+(y^2+4y)=20\\\\(x^2+2x+1)+(y^2+4y)=20+1\\\\(x^2+2x+1)+(y^2+4y+4)=20+1+4\\\\(x+1)^2 + (y+2)^2 = 25$

center = (h,k) = (-1,-2)

radius = 5

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Explanation:

I grouped up the x and y terms separately. Then I added 1 to both sides to complete the square for the x terms. I cut the 2 from 2x in half, then squared it to get 1. In the next step, I cut the 4 from 4y in half to get 2, which squares to 4. So that's why I added 4 to both sides to complete the square for the y terms.

Each piece is factored using the perfect squares factoring rule which is a^2+2ab+b^2 = (a+b)^2

The last equation is in the form (x-h)^2 + (y-k)^2 = r^2

We can think of x+1 as x - (-1) to show that h = -1

Similarly, y+2 = y-(-2) = y-k to show that k = -2

The center is (h,k) = (-1,-2)

The radius is r = 5 because r^2 = 5^2 = 25 is on the right hand side in the last equation above.