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S(x, y) = 0  represents a circle. The equation S(x, 2) = 0 gives two identical solutions x = 1 and the equation S(1, y) = 0 gives two distinct solutions y=0,2. Find the equation of the circle.

Option: 1

x^{2}+y^{2}+2x-2y+1=0


Option: 2

x^{2}+y^{2}-2x+2y+1=0


Option: 3

x^{2}+y^{2}-2x-2y-1=0


Option: 4

x^{2}+y^{2}-2x-2y+1=0


Answers (1)

best_answer

 

Equation of a circle in diametric form -

\left ( x-x_{1} \right )\left ( x-x_{2} \right )+\left ( y-y_{1} \right )\left ( y-y_{2} \right )= 0

 

- wherein

Where A\left ( x_{1},y_{1} \right )\, and \:B \left ( x_{2},y_{2} \right ) are the two diametric ends.

 

 

S(x, 2) = 0 given two identical solutions x = 1.

\Rightarrowline y = 2 is a tangent to the circle S(x, y) = 0 at the point (1, 2)  and S(1, y) = 0 gives two distinct                 solutions y = 0, 2

\RightarrowLine x = 1 cut the circle S(x, y) = 0 at points (1, 0)  and (1, 2)           

 

 

A(1, 2) and B(1, 0) are diametrically opposite points.

\therefore equation of the circle is \left ( x-1 \right )^{2}+y\left ( y-2 \right )=0

x^{2}+y^{2}-2x-2y+1=0

 

Posted by

Suraj Bhandari

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