Question 521802
All of these equations don't have real solutions, so i assume you are were introduced to i=sqrt(-1). 

1. -6x^2=30
x^2=-5
X1=i*sqrt(5)
X2=-i*sqrt(5)

2. 3x^2=-18
x1=i*sqrt(6)
x2=-i*sqrt(6)

3. x^2=-45
x1=3i*sqrt(5)
x2=-3i*sqrt(5)