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