Answer
$4.472i$
Work Step by Step
Step 1: $\sqrt {-20}$
Step 2: $\sqrt {-1\times20}$
Step 3: $\sqrt {-1}\times\sqrt {20}$
Step 4: $\sqrt {-1}\times\sqrt {4\times5}$
Step 5: $\sqrt {-1}\times\sqrt 4\times\sqrt 5$
Step 6: As $i=\sqrt {-1}$,$\sqrt {-1}\times\sqrt 4\times\sqrt 5=i\times2\times\sqrt 5$
Step 7: $i\times2\times\sqrt 5=2i\sqrt 5\approx4.472i$
