Question 1 : Umm to find the values of x you would need to let y = 0. SBS square both side leaves (x-6)(3-x)(x+4) = 0 values of x are 6, 3 and -4. As for the function not sure what it's called :P
Question 2: Use polynomials or try and factorise it by completing the square some how.
Question 3...