If z = x + iy, where i = √-1, then what does the equations zz̅ + ∣z2 + 4(z + z̅) - 48 = 0 represent?

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NDA 02/2021: Maths Previous Year paper (Held On 14 Nov 2021)
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  1. Straight line
  2. Parabola
  3. Circle
  4. Pair of straight lines

Answer (Detailed Solution Below)

Option 3 : Circle
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Detailed Solution

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Formula used:

z = a + ib

Equation of circle: (x - h)2 + (y - k)2 = r2

Where (h,k) is the coordinates of center of the circle and r is the radius. 

Calculation:

we have 

(x + iy)(x - iy) + x2 + y2 + 4(x + iy + x - iy) - 48 = 0

⇒ x2 + y2 +  x2 + y2 + 4 × 2x - 48 = 0

⇒ 2(x2 + y2) + 8x - 48 = 0

⇒ x2 + y2 + 4x - 24 = 0

⇒ (x + 2)2 + (y - 0)2 = 

Since, the above equation is similar to (x - h)2 + (y - k)2 = r2

∴ The given equation represent a circle.

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