Question 49886
a. X^2 = -100 
There are no Real Numbers whose square is negative.
There are Complex Numbers that do the job.
For your problem 
X= 10i or -10i where "i" is the square root of -1.
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b. 5X^2 = -125
X^2=-25
X=5i or X=-5i
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Cheers
Stan H.