\(f(x)= x^{4} - x^{3} - 28x^{2} - 20x + 48\)
There are two changes of sign, so there are 2 or 0 possible positive roots.
\(f(-x)= x^{4} +x^{3} - 28x^{2}+ 20x + 48\)
There are two changes of sign, so there are 2 or 0 possible negative roots.
There are 4,2 or 0 possible non-real roots.