If `z=(3+7i)(a+ib)`, where `a`, `b in Z-{0}`, is purely imaginery, then minimum value of `|z|^(2)` is
If `z=(3+7i)(a+ib)`, where `a`, `b in Z-{0}`, is purely imaginery, then minimum value of `|z|^(2)` is
A. `74`
B. `45`
C. `65`
D. `58`
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Correct Answer - D
`(d)` `z=(3a-7b)+i(3b+7a)`
For purely imaginary, `3a=7b`
`impliesa=7` or `b=3` (for least value of `|z|`)
`implies |z|=|3+7i|=sqrt(58)`
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