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If the length of the tangent from (h,k) ...

If the length of the tangent from (h,k) to the circle `x^(2)+y^2=16` is twice the length of the tangent from the same point to the circle `x^(2)+y^(2)+2x+2y=0`, then

A

`h^(2)+k^(2)_4h+4k+16=0`

B

`h^(2)+k^(2)+3h+3k=0`

C

`3h^(2)+3k^(2)+8y+8k+16=0`

D

`3h^(2)+3k^(2)+4h+4k+16=0`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the relationship between the point \((h, k)\) and the two circles given. ### Step-by-Step Solution: 1. **Identify the equations of the circles:** - The first circle is given by the equation \(x^2 + y^2 = 16\). - The second circle is given by the equation \(x^2 + y^2 + 2x + 2y = 0\). We can rewrite this as \(x^2 + y^2 + 2x + 2y + 4 = 4\), which simplifies to \((x + 1)^2 + (y + 1)^2 = 4\). This means the center of the second circle is at \((-1, -1)\) with a radius of \(2\). 2. **Calculate the lengths of the tangents:** - The length of the tangent from a point \((h, k)\) to the first circle is given by the formula: \[ L_1 = \sqrt{h^2 + k^2 - 16} \] - The length of the tangent from the same point \((h, k)\) to the second circle is: \[ L_2 = \sqrt{(h + 1)^2 + (k + 1)^2 - 4} \] 3. **Set up the relationship between the lengths:** - According to the problem, the length of the tangent to the first circle is twice that of the second circle: \[ L_1 = 2L_2 \] - Substituting the expressions for \(L_1\) and \(L_2\): \[ \sqrt{h^2 + k^2 - 16} = 2\sqrt{(h + 1)^2 + (k + 1)^2 - 4} \] 4. **Square both sides to eliminate the square roots:** \[ h^2 + k^2 - 16 = 4\left((h + 1)^2 + (k + 1)^2 - 4\right) \] 5. **Expand the right-hand side:** - Expanding \((h + 1)^2\) gives \(h^2 + 2h + 1\). - Expanding \((k + 1)^2\) gives \(k^2 + 2k + 1\). - Thus, we have: \[ h^2 + k^2 - 16 = 4(h^2 + 2h + 1 + k^2 + 2k + 1 - 4) \] - Simplifying the right-hand side: \[ = 4(h^2 + k^2 + 2h + 2k - 2) = 4h^2 + 4k^2 + 8h + 8k - 8 \] 6. **Rearranging the equation:** - Bringing all terms to one side: \[ h^2 + k^2 - 16 - 4h^2 - 4k^2 - 8h - 8k + 8 = 0 \] - This simplifies to: \[ -3h^2 - 3k^2 - 8h - 8k - 8 = 0 \] - Multiplying through by \(-1\): \[ 3h^2 + 3k^2 + 8h + 8k + 8 = 0 \] 7. **Final equation:** - Dividing through by 3 gives: \[ h^2 + k^2 + \frac{8}{3}h + \frac{8}{3}k + \frac{8}{3} = 0 \] ### Conclusion: The required equation is: \[ 3h^2 + 3k^2 + 8h + 8k + 8 = 0 \]
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