Question:medium

The equation of the sphere passing through \((1,0,0),(0,1,0),(0,0,1)\) and has its centre on the plane \(x+y+z=6\) is

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For a sphere \(x^2+y^2+z^2+2ux+2vy+2wz+d=0\), centre is \((-u,-v,-w)\).
  • \(x^2+y^2+z^2+4x-4y-4z-3=0\)
  • \(x^2+y^2+z^2-4x-4y+4z+3=0\)
  • \(x^2+y^2+z^2-4x-4y-4z-3=0\)
  • \(x^2+y^2+z^2-4x-4y-4z+3=0\)
Show Solution

The Correct Option is D

Solution and Explanation

Step 1: Understanding the Concept:
We need to find the equation of a sphere that satisfies four conditions: passing through three given points and having its center on a given plane.

Step 2: Key Formula or Approach:

1. Let the general equation of the sphere be \(x^2+y^2+z^2+2ux+2vy+2wz+d=0\). 2. Substitute the coordinates of the three given points into this equation to get three linear equations in u, v, w, and d. 3. The center of the sphere is \((-u, -v, -w)\). This point lies on the plane \(x+y+z=6\), which gives a fourth linear equation: \(-u-v-w=6\). 4. Solve the system of four linear equations to find u, v, w, and d. 5. Substitute these values back into the general equation of the sphere.

Step 3: Detailed Explanation:

Let the equation of the sphere be \(x^2+y^2+z^2+2ux+2vy+2wz+d=0\). The sphere passes through the following points: Point (1,0,0): \[ (1)^2+0+0+2u(1)+0+0+d=0 \implies 1+2u+d=0 \quad (1) \] Point (0,1,0): \[ 0+(1)^2+0+0+2v(1)+0+d=0 \implies 1+2v+d=0 \quad (2) \] Point (0,0,1): \[ 0+0+(1)^2+0+0+2w(1)+d=0 \implies 1+2w+d=0 \quad (3) \] From (1), (2), and (3), we can see that: \[ 1+2u+d = 1+2v+d \implies 2u=2v \implies u=v \] \[ 1+2v+d = 1+2w+d \implies 2v=2w \implies v=w \] So, we have \(u=v=w\). The center of the sphere is \((-u,-v,-w)\). This point lies on the plane \(x+y+z=6\). \[ (-u) + (-v) + (-w) = 6 \implies -u-v-w = 6 \] Since \(u=v=w\), we can substitute: \[ -u-u-u = 6 \implies -3u = 6 \implies u = -2 \] Therefore, \(u=v=w=-2\). Now, use equation (1) to find d: \[ 1+2u+d=0 \implies 1+2(-2)+d=0 \implies 1-4+d=0 \implies -3+d=0 \implies d=3 \] We have found all the coefficients: \(u=-2, v=-2, w=-2, d=3\). Substitute these into the general equation of the sphere: \[ x^2+y^2+z^2+2(-2)x+2(-2)y+2(-2)z+3=0 \] \[ x^2+y^2+z^2-4x-4y-4z+3=0 \]

Step 4: Final Answer:

The equation of the sphere is \(x^2+y^2+z^2-4x-4y-4z+3=0\), which corresponds to option (D).
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