How do you find a real root of an equation? I thought when you get the roots for example y=(x-3)(x+2)(x-7) the roots would be 3,-2, and 7. I'm not sure of how to know if it is "real" or not.

How would you go about finding the real root of (5x^2+20)(3x^2-48)=0

and (2x^2-x-13)(x^2+1)= 0