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For a complex number Z, if the argument ...

For a complex number Z, if the argument of `3+3i and (Z-2) (bar(Z)-1)` are equal, then the maximum distance of Z from the x - axis is equal to (where, `i^(2)=-1`)

A

`((1+sqrt2))/(2)" units"`

B

`2" units"`

C

`(3)/(2)" units"`

D

`((sqrt2+2))/(2)" units"`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the maximum distance of the complex number \( Z \) from the x-axis, given that the arguments of \( 3 + 3i \) and \( (Z - 2)(\bar{Z} - 1) \) are equal. ### Step 1: Define the complex number Let \( Z = x + iy \), where \( x \) and \( y \) are real numbers. ### Step 2: Calculate \( Z - 2 \) and \( \bar{Z} - 1 \) We have: \[ Z - 2 = (x - 2) + iy \] \[ \bar{Z} = x - iy \quad \text{so} \quad \bar{Z} - 1 = (x - 1) - iy \] ### Step 3: Calculate the product \( (Z - 2)(\bar{Z} - 1) \) Now, we compute: \[ (Z - 2)(\bar{Z} - 1) = [(x - 2) + iy][(x - 1) - iy] \] Using the distributive property: \[ = (x - 2)(x - 1) - (x - 2)iy + iy(x - 1) + y^2 \] \[ = (x^2 - 3x + 2 + y^2) + i(y(x - 1) - (x - 2)) \] \[ = (x^2 - 3x + 2 + y^2) + i(yx - y - x + 2) \] ### Step 4: Find the argument of \( 3 + 3i \) The argument of \( 3 + 3i \) is given by: \[ \text{arg}(3 + 3i) = \tan^{-1}\left(\frac{3}{3}\right) = \tan^{-1}(1) = \frac{\pi}{4} \] ### Step 5: Set the arguments equal For the arguments to be equal: \[ \frac{yx - y - x + 2}{x^2 - 3x + 2 + y^2} = 1 \] This implies: \[ yx - y - x + 2 = x^2 - 3x + 2 + y^2 \] ### Step 6: Rearranging the equation Rearranging gives: \[ yx - y - x + 2 - (x^2 - 3x + 2 + y^2) = 0 \] \[ yx - y - x - x^2 + 3x - y^2 = 0 \] \[ -x^2 + (y + 3)x - y - y^2 = 0 \] ### Step 7: Identify the circle This is a quadratic equation in \( x \). The discriminant must be non-negative for real solutions: \[ D = (y + 3)^2 - 4(-1)(-y - y^2) \geq 0 \] \[ D = (y + 3)^2 - 4y - 4y^2 \geq 0 \] \[ D = -3y^2 + 2y + 9 \geq 0 \] ### Step 8: Find the maximum distance from the x-axis The maximum distance of \( Z \) from the x-axis is the maximum value of \( y \). To find this, we need to solve the quadratic inequality: \[ -3y^2 + 2y + 9 \geq 0 \] Using the quadratic formula: \[ y = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} = \frac{-2 \pm \sqrt{(2)^2 - 4(-3)(9)}}{2(-3)} \] \[ = \frac{-2 \pm \sqrt{4 + 108}}{-6} = \frac{-2 \pm \sqrt{112}}{-6} = \frac{-2 \pm 4\sqrt{7}}{-6} \] \[ = \frac{2 \mp 4\sqrt{7}}{6} = \frac{1 \mp 2\sqrt{7}}{3} \] The maximum value occurs at: \[ y = \frac{1 + 2\sqrt{7}}{3} \] ### Final Answer Thus, the maximum distance of \( Z \) from the x-axis is: \[ \frac{1 + 2\sqrt{7}}{3} \]
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