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The coordinates of the centre and radius...

The coordinates of the centre and radius of the circle represented by the equation
`(3-2lambda)x^(2)+lambda y^(2)-4x+2y-4=0` are

A

(2, 1), 3

B

(-2, 1), 3

C

(2, 1), 3

D

(2, -1), 1

Text Solution

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The correct Answer is:
To find the coordinates of the center and the radius of the circle represented by the equation \[ (3 - 2\lambda)x^2 + \lambda y^2 - 4x + 2y - 4 = 0, \] we will follow these steps: ### Step 1: Identify the coefficients The equation can be rewritten in the standard form of a circle. For that, we need to ensure that the coefficients of \(x^2\) and \(y^2\) are equal. The coefficient of \(x^2\) is \(3 - 2\lambda\) and the coefficient of \(y^2\) is \(\lambda\). For the equation to represent a circle, we set these coefficients equal: \[ 3 - 2\lambda = \lambda. \] ### Step 2: Solve for \(\lambda\) Rearranging the equation gives: \[ 3 = 3\lambda \implies \lambda = 1. \] ### Step 3: Substitute \(\lambda\) back into the equation Now, substitute \(\lambda = 1\) back into the original equation: \[ (3 - 2 \cdot 1)x^2 + 1 \cdot y^2 - 4x + 2y - 4 = 0, \] which simplifies to: \[ (3 - 2)x^2 + y^2 - 4x + 2y - 4 = 0 \implies x^2 + y^2 - 4x + 2y - 4 = 0. \] ### Step 4: Rearrange the equation Next, we rearrange the equation to group the \(x\) and \(y\) terms: \[ x^2 - 4x + y^2 + 2y = 4. \] ### Step 5: Complete the square Now, we complete the square for the \(x\) and \(y\) terms. For \(x^2 - 4x\): \[ x^2 - 4x = (x - 2)^2 - 4. \] For \(y^2 + 2y\): \[ y^2 + 2y = (y + 1)^2 - 1. \] Substituting these back into the equation gives: \[ (x - 2)^2 - 4 + (y + 1)^2 - 1 = 4. \] ### Step 6: Simplify the equation Now, simplifying this: \[ (x - 2)^2 + (y + 1)^2 - 5 = 4 \implies (x - 2)^2 + (y + 1)^2 = 9. \] ### Step 7: Identify the center and radius This is now in the standard form of a circle: \[ (x - h)^2 + (y - k)^2 = r^2, \] where \((h, k)\) is the center and \(r\) is the radius. From our equation: - The center \((h, k) = (2, -1)\). - The radius \(r = \sqrt{9} = 3\). ### Final Answer Thus, the coordinates of the center are \((2, -1)\) and the radius is \(3\). ---

To find the coordinates of the center and the radius of the circle represented by the equation \[ (3 - 2\lambda)x^2 + \lambda y^2 - 4x + 2y - 4 = 0, \] we will follow these steps: ...
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OBJECTIVE RD SHARMA ENGLISH-CIRCLES-Chapter Test
  1. The coordinates of the centre and radius of the circle represented by ...

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  2. The two circles x^2 + y^2 -2x+6y+6=0 and x^2 + y^2 - 5x + 6y + 15 = 0 ...

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  3. The two circles x^(2)+y^(2)-2x-2y-7=0 and 3(x^(2)+y^(2))-8x+29y=0

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  4. The centre of a circle passing through (0,0), (1,0) and touching the C...

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  5. The circle x^2+y^2=4 cuts the circle x^2+y^2+2x+3y-5=0 in A and B, The...

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  6. One of the limit point of the coaxial system of circles containing x^(...

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  7. A circle touches y-axis at (0, 2) and has an intercept of 4 units on t...

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  8. The equation of the circle whose one diameter is PQ, where the ordinat...

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  9. The circle x^(2)+y^(2)+4x-7y+12=0 cuts an intercept on Y-axis is of le...

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  10. Prove that the equation of any tangent to the circle x^2+y^2-2x+4y-4=0...

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  11. The angle between the pair of tangents from the point (1, 1/2) to the...

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  12. The intercept on the line y=x by the circle x^(2)+y^(2)-2x=0 is AB. Eq...

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  13. If 3x+y=0 is a tangent to a circle whose center is (2,-1) , then find ...

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  14. The locus of the midpoint of a chord of the circle x^2+y^2=4 which sub...

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  15. Two tangents to the circle x^(2) +y^(2) = 4 at the points A and B meet...

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  16. A tangent is drawn to the circle 2(x^(2)+y^(2))-3x+4y=0 and it touch...

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  17. the length of the chord of the circle x^(2)+y^(2)=25 passing through ...

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  18. If the points A(2, 5) and B are symmetrical about the tangent to the c...

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  19. The equation of the circle of radius 2 sqrt(2) whose centre lies on th...

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  20. Prove that the maximum number of points with rational coordinates on a...

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  21. The equation of a circle C is x^(2)+y^(2)-6x-8y-11=0. The number of re...

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