SOLUTION: Let C be the circle with equation x^2+2y-9=-y^2+18x+9. If (a,b) is the center of C and r is its radius, what is the value of a+b+r? Thank you for helping me!

Algebra ->  Expressions-with-variables -> SOLUTION: Let C be the circle with equation x^2+2y-9=-y^2+18x+9. If (a,b) is the center of C and r is its radius, what is the value of a+b+r? Thank you for helping me!       Log On


   

Question 1030080: Let C be the circle with equation x^2+2y-9=-y^2+18x+9. If (a,b) is the center of C and r is its radius, what is the value of a+b+r?

Thank you for helping me!
Answer by josgarithmetic(39630) About Me  (Show Source):
You can put this solution on YOUR website!
Adjust the equation into standard form and read the center and radius directly. Completion of Square may be necessary...

x%5E2-18x%2By%5E2%2B2y-9-9=0
x%5E2-18x%2By%5E2%2B2y=18

The term for x is %2818%2F2%29%5E2=81 and the term for y is 1.
Check the lesson about this if you need to.

x%5E2-18x%2B81%2By%5E2%2B2y%2B1=18%2B81%2B1

highlight%28%28x-9%29%5E2%2B%28y%2B1%29%5E2=100%29
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Center of Circle,  (9,-1)
Radius size is 10 or square root of 100.