Been having some difficulty with the following question:
Prove that if the roots of:
x^3-ax^2+bx-c=0 are in arithmetic sequence then 2a^3-9ab+27c=0
Hence, solve for x in the equation x^3 -12x^2+39x -28=0
I've tried putting general forms of the roots as:
and then substituting them into the initial equation and setting = 0, but it hasn't gotten me anywhere.
Any help would be greatly appreciated