AP EAMCET · Maths · Circle

Find the equation of the circle which passes through the point $(1, 2)$ and the points of intersection of the circles $x^{2} + y^{2} - 8 x - 6 y + 21 = 0$ and $x^{2} + y^{2} - 2 x - 15 = 0$ .

A $x^{2} + y^{2} - 18 x - 12 y + 27 = 0$
B $2 (x^{2} + y^{2}) - 18 x - 12 y + 27 = 0$
C $3 (x^{2} + y^{2}) - 18 x - 12 y + 27 = 0$
D $4 (x^{2} + y^{2}) - 18 x - 12 y + 27 = 0$

Verified Solution

Answer & Solution

Correct Answer

(C) $3 (x^{2} + y^{2}) - 18 x - 12 y + 27 = 0$

Step-by-step Solution

Detailed explanation

Let S1=x2+y2-8x-6y+21=0 & S2=x2+y2-2x-15=0 Using family of circles S1+λS2=0 x2+y2-8x-6y+21+λx2+y2-2x-15=0 Since it passes through 1,2 1+4-8-62+21+λ1+4-21-15=0 26-20+λ5-17=0 6+λ-12=0 λ=12 So, the equation is…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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Find the equation of the circle which passes through the point (1,2) and the points of intersection of the circles x2+y2-8x-6y+21=0 and x2+y2-2x-15=0.

Step-by-step Solution

Find the equation of the circle which passes through the point $(1, 2)$ and the points of intersection of the circles $x^{2} + y^{2} - 8 x - 6 y + 21 = 0$ and $x^{2} + y^{2} - 2 x - 15 = 0$ .