Gy, this is the solution to # 11 and # 12:
Let's recall that √-1 = i
11. √-81
√-1 * 81 (-1 * 81= -81)
9√-1
9i
12. √-50
√-2 * 25 (-2 * 25 = -50)
5√-2
5i√2
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