The equation of the circle having its centre on the line x + 2y - 3 = ...
Solution:
Finding the Center of the Circle:
We are given that the center of the circle lies on the line x - 2y - 3 = 0. Let's find the coordinates of the center.
- The given line can be written in the standard form as, x - 2y = 3.
- Let's assume that the center of the circle is (h, k). Then the equation of the line passing through (h, k) and perpendicular to the given line is given by:
(y - k) = (1/2)(x - h)
- Simplifying this equation, we get: x - 2y - (h - 2k) = 0
- Since this line passes through (h, k), we have: h - 2k = 3
- We have two equations in two variables: x - 2y = 3 and h - 2k = 3. Solving these equations, we get: h = 3, k = 0.
- Therefore, the center of the circle is (3, 0).
Finding the Radius of the Circle:
We are given that the circle passes through the points of intersection of the circles x^2 + y^2 - 2x - 4y + 1 = 0 and x^2 + y^2 - 4x - 2y + 4 = 0. Let's find these points of intersection.
- Subtracting the second equation from the first, we get: 2x + 2y - 3 = 0.
- Simplifying this equation, we get: y = -(x/2) + 3/2.
- Substituting this value of y in the first equation and simplifying, we get: x^2 - 2x + 1 = 0.
- Solving this quadratic equation, we get: x = 1 (repeated root).
- Substituting this value of x in y = -(x/2) + 3/2, we get: y = 1.
- Therefore, the two points of intersection are (1, 1) and (1, -1).
- The distance between the center of the circle (3, 0) and either of these points of intersection is the radius of the circle. Using the distance formula, we get: r = 2.
Writing the Equation of the Circle:
- The equation of a circle with center (h, k) and radius r is given by: (x - h)^2 + (y - k)^2 = r^2.
- Substituting the values of (h, k, r), we get: (x - 3)^2 + y^2 = 4.
- Simplifying this equation, we get: x^2 + y^2 - 6x + 9 = 0.
- Subtracting 9 from both sides, we get: x^2 + y^2 - 6x = -9.
- Adding 9 and 36 to both sides (to complete the square), we get: x^2 - 6x + 9 + y^2 = 27.
- Simplifying this equation, we get: (x - 3)^2 + y^2 = 27.
- Therefore, the equation of the circle is: x^
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