SOLUTION: x^2 + y^2 - 4x + 2y = 15 i) Find the coordinates of the centre C of the cirlce and the radius of the circle ii)Show that the point P (4, -5 ) lies in the circle iii) Find the

Algebra ->  Customizable Word Problem Solvers  -> Geometry -> SOLUTION: x^2 + y^2 - 4x + 2y = 15 i) Find the coordinates of the centre C of the cirlce and the radius of the circle ii)Show that the point P (4, -5 ) lies in the circle iii) Find the       Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 674682: x^2 + y^2 - 4x + 2y = 15
i) Find the coordinates of the centre C of the cirlce and the radius of the circle
ii)Show that the point P (4, -5 ) lies in the circle
iii) Find the equation of the tangent to the circle at the point P
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi

x^2 + y^2 - 4x + 2y = 15

x^2 - 4x + 4 + y^2 + 2y + 1 = 15 + 4 + 1

%28x-2%29%5E2+%2B+%28y%2B1%29%5E2+=+20  C(2,-1)  r = sqrt(20) = 2sqrt(5)

 C(2,-1)

  (4,-5)  m = 4/-2 = -2

tangent Line  m = 1/2

 y = (1/2)x + b   ||Using the  (x,y) ordered pair (4,-5) to solve for b

-5 =(1/2)4 + b

-7 = b

 y = (1/2)x -7