SOLUTION: I just want to check if my answer is correct. The problem is: Find the center of the circle passing through (9,-2),(2,5),(-3,6). My answer is: (-3,-7)

Algebra ->  Length-and-distance -> SOLUTION: I just want to check if my answer is correct. The problem is: Find the center of the circle passing through (9,-2),(2,5),(-3,6). My answer is: (-3,-7)      Log On


   



Question 923980: I just want to check if my answer is correct.
The problem is: Find the center of the circle passing through (9,-2),(2,5),(-3,6).
My answer is: (-3,-7)

Found 2 solutions by jim_thompson5910, MathTherapy:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
You are correct. I used the program GeoGebra to confirm the answer and I also got (-3,-7). Nice work.

Answer by MathTherapy(10551) About Me  (Show Source):
You can put this solution on YOUR website!

I just want to check if my answer is correct.
The problem is: Find the center of the circle passing through (9,-2),(2,5),(-3,6).
My answer is: (-3,-7)

That's correct!!
Plug each point into the center-radius equation, since each radius will have the same center point
(h, k), and radius, r

(9, - 2)

%28x+-+h%29%5E2++%2B+%28y+-+k%29%5E2+=+r%5E2
%289+-+h%29%5E2++%2B+%28-+2+-+k%29%5E2+=+r%5E2
81+-+18h+%2B+h%5E2+%2B+4+%2B+4k+%2B+k%5E2+=+r%5E2
h%5E2+-+18h+%2B+k2+%2B+4k+-+r%5E2+=+-+85 ------- eq (i)

(2, 5)

%28x+-+h%29%5E2++%2B+%28y+-+k%29%5E2+=+r%5E2+
%282+-+h%29%5E2++%2B+%285+-+k%29%5E2++=++r%5E2+
4+-+4h+%2B+h%5E2+%2B+25+-+10k+%2B+k%5E2+=+r%5E2
h%5E2+-+4h+%2B+k%5E2+-+10k+-+r%5E2+%2B+4+%2B+25+=+0
h%5E2+-+4h+%2B+k%5E2+-+10k+-+r%5E2+=+-+29 ------- eq (ii)

(- 3, 6)

%28x+-+h%29%5E2++%2B+%28y+-+k%29%5E2+=+r%5E2
%28-+3+-+h%29%5E2++%2B+%286+-+k%29%5E2++=++r%5E2+
9+%2B+6h+%2B+h%5E2+%2B+36+-+12k+%2B+k%5E2+=+r%5E2
h%5E2+%2B+6h+%2B+k%5E2+-+12k+-+r%5E2+%2B+9+%2B+36+=+0
h%5E2+%2B+6h+%2B+k%5E2+-+12k+-+r%5E2+=+-+45 ------- eq (iii)
h%5E2+-+18h+%2B+k2+%2B+4k+-+r%5E2+=+-+85 ------- eq (i)
h%5E2+-+4h+%2B+k%5E2+-+10k+-+r%5E2+=+-+29 ------ eq (ii)
– 14h + 14k = - 56 ------ Subtracting eq (ii) from eq (i)
– 14(h - k) = - 14(4)
h - k = 4 ----------- eq (iv)
h%5E2+-+4h+%2B+k%5E2+-+10k+-+r%5E2+=+-+29 ------ eq (ii)
h%5E2+%2B+6h+%2B+k%5E2+-+12k+-+r%5E2+=+-+45 ------ eq (iii)
– 10h + 2k = 16 ------ Subtracting eq (iii) from eq (ii)
- 2(5h - k) = - 2(- 8)
5h - k = - 8 --------- eq (v)
h - k = 4 -------- eq (iv)
5h - k = - 8 -------- eq (v)
- 4h = 12 -------- Subtracting eq (v) from eq (iv)
h+=+12%2F%28-+4%29, or – 3
- 3 - k = 4 ----- Substituting - 3 for h in eq (iv)
- k = 4 + 3
– k = 7
k+=+7%2F%28-+1%29, or - 7
With h = - 3, and k = - 7, center coordinate point (h, k) is: highlight_green%28highlight_green%28system+%28h+=+-+3%2C+k+=+-+7%29%29%29