Question 207197
1. 4-5 square root of -6
{{{4 - 5sqrt(-6)}}}
= {{{4 - 5sqrt(-1)*sqrt(6)}}}
= {{{4 - 5isqrt(6)}}}
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That's all can be done.  i is the sqrt (-1), so separate if from the 6.
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2. 3+ the square root of -7
{{{3 + sqrt(-7)}}}
= {{{3 + sqrt(-1)*sqrt(7)}}}
= {{{3 + isqrt(7)}}}
No reason to panic.