Question 1195879
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Recall that {{{i = sqrt(-1)}}} by definition of what it means to be an imaginary number. 


So,
{{{sqrt(-9) = sqrt(-1*9)}}}

 
{{{sqrt(-9) = sqrt(-1)*sqrt(9)}}}

 
{{{sqrt(-9) = i*3}}}

 
{{{sqrt(-9) = 3i}}}
We do not involve the plus/minus in this case. This is because the result of the square root function is one output only.
Input = -9 leads to output = 3i


Therefore,
{{{sqrt(-9) - 6 = 3i - 6 = -6+3i}}}
The complex number is of the form a+bi
a = -6 = real part
b = 3 = imaginary part
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