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MathsHardNumerical2022 · 29 Jul Shift 1

Q86.Let the mirror image of a circle c1 : x2 + y2 −2x −6y + α = 0 in line y = x + 1 be c2 : 5x2 + 5y2 + 10gx +10fy + 38 = 0. If r is the radius of circle c2 , then α + 6r2 is equal to ______

What This Question Tests

This question tests the ability to find the mirror image of a circle across a given line, relate the properties of the original and reflected circles, and use the standard equation of a circle.

Concepts Tested

Equation of a circleReflection of a point across a lineRadius of a circle

Formulas Used

Center of (x-h)^2 + (y-k)^2 = r^2 is (h,k)

Reflection of (x,y) in y=x+c

Radius = sqrt(g^2+f^2-c)

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