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Question) If $|z_1 -1|<1$, $|z_2 -2|<2$, $|z_3 -3|<3$ then $|z_1+z_2+z_3|$ is:

(a) is less than 6
(b) is more than 3
(c) is less than 12
(d) lies between 6 and 12

My Attempt:

(1) Using polygon inequality $|z_1+z_2+z_3|<|z_1|+|z_2|+|z_3|$. I got maximum value =12.

(2)For finding minimum value i plotted three circles with centres at (1,0), (2,0) and (3,0) all passing through origin. Then i considered $z_1,z_2,z_3$ to be lying inside the smallest circle and then arrived at the conclusion that $|z_1+z_2+z_3|\geq0$.
enter image description here

Hence I'm getting option (c) as answer but answer key says option (b) to be the correct answer. Is my way of analysis via graph wrong?

Sujith Sizon
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0 Answers0