If x2 - 4 = 45, then x could be equal to 9 3 5 -7 -4

Transpose the constant on the left hand side of the equation to the right side. The equation becomes x² = 45 + 4, 
                                               x² = 49
                                           x = sqrt(49) 
                                            x = 7 and x = -7
Only -7 is on the choices. Thus, the answer is x = -7.

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