Question 1115076
<br>
{{{sqrt(-8)*sqrt(-10) = (i*sqrt(8))*(i*sqrt(10)) = (i^2)*sqrt(80) = (-1)*sqrt(80) = (-1)*(4*sqrt(5)) = -4*sqrt(5)}}}<br>
You MUST factor out the square root of -1 from each factor before multiplying.  The rule<br>
{{{sqrt(a)*sqrt(b) = sqrt(ab)}}}<br>
does NOT apply if both a and b are negative.