If the product of two of the roots of $x^4-5x^3+5x^2+5x-6=0$  is 3 then the roots are

So, 1 is a root

Sum of even power coefficient $=$  Sum of odd power coefficient

$1+5-6=5-5$

$0=0$

So, $-1$  is a root

The roots are  $\pm 1,2,3$   ( By option verification method)