Question 394198
1) If z=3-4i then 
|z|= sqrt[3^2 + 4^2] = sqrt[25] = 5
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2) If z=8-sqrt(39)i then 
|z|= sqrt[8^2+ sqrt(39)^2] 
= sqrt[64+39]
= sqrt(103)
= 10.15

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Cheers,
Stan H.