Answer: choice A) plus or minus the square root of 10
We apply the square root to both sides of x^2 = 10 to get x = sqrt(10) or x = -sqrt(10). The plus or minus is from the fact that squaring a negative gives you a positive.
Another example: x^2 = 9 means x = 3 or x = -3 since (-3)^2 = 9 and (3)^2 = 9
