## College Algebra (6th Edition)

$\sqrt -20=i\sqrt 20 = i\sqrt (4 \times 5) = 2i\sqrt 5$
Using $\sqrt -b = i\sqrt b$ $\sqrt -20=i\sqrt 20$ $= i\sqrt (4 \times 5)$ $=i \sqrt 4 \times \sqrt 5$ $= 2i\sqrt 5$