Answer:
x = ±√10i (i outside the radical), or approximately ±3.62i, or no solution depending on your class.
Explanation:
x^2 + 10 = 0
x^2 = -10
x = ±√-10
x = ±√10i (i outside the radical), or approximately ±3.62i.
The solution is not real.
If you meant x^2 - 10 = 0 then x = ±√10 or approximately ±3.62. This solution is real.