Solve square root
x^2+12x+43=0

X²+12x+43=0

This a quadratic equation ax²+bx+c=0 (in our case a=1, b=12, & c=43)

to solve it, means to calculate the value of x which render this equation nil

In short we have to find the roots x' & x'' by applying the following formula:

x' = [-b+√(b² - 4ac)] / 2a  & x" =[-b - √(b² - 4ac)] / 2a 
If you plug the related values you will notice the amount inside the radical (√)
is negative. As you know such an amount should be positif, hence their is no roots & consequently no solution