JEE Main2014MathematicsComplex NumberActual
If z is a complex number such that z ≥ 2 , then the minimum value of z + 1 2 :
Options
- AIs strictly greater than 5 2
- BIs strictly greater than 3 2 but less than 5 2
- CIs equal to 5 2
- DLies in the interval ( 1 ,   2 )
Correct answer
D. Lies in the interval ( 1 ,   2 )
Step-by-step solution
z ≥ 2     i . e .,   z - 0 ≥ 2 ∴ The distance of ' z ' from origin is greater than two. We have to find minimum of z + 1 2 z + 1 2 = z - - 1 2 = distance of z from - 1 2 ,   0 . On the argand plane, z lies in the dotted regions I ,   II ,   III ,   IV . ∴ The minimum distance is from the point B = 2 - 1 2 = 3 2 ⇒ 3 2 ∈ 1 ,   2