Q31 / 108 · NTA Abhyas (JEE Main) 2020 · Mathematics · Complex Number

For the complex number z satisfying the condition  z+2z =2, the maximum value of  z  is

  • A
    3-1
  • Correct answer
    B
    3+1
  • C
    2+3
  • D
    3

Solution

|z|−|2|z||≤|z+2z|≤|z|+|2|z||

Now, for maximum or minimum value of |z|, LHS inequality will hold true as it corresponds to the two complex numbers being on opposite sides of origin.

Hence,  | z |− 2 | z | ≤2 (without loss of generality let LHS > 0)

⇒|z|2−2|z|−2≤0

⇒| z |≤ 2+ 4+8 2

⇒| z |≤1+ 3

Hence, the correct answer is option: 'B'.

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