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If z = (3+ 7i) (a +ib) where a,b in in Z...

If `z = (3+ 7i) (a +ib)` where a,`b in in Z- {0}`, is purely imaginary , then the minimum value of `|z|` is

A

74

B

45

C

58

D

65

Text Solution

Verified by Experts

The correct Answer is:
C
`z=(3a-7b)+i(3b+7a)`
For z to be purely imaginary, we have
`3a=7b`
`rArra =7 or b=3` (for least value of `|z|`)
`rArr |z| =|3+7i|`
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