Why is x-5 not a factor of - 3x^4 + 15x^3 - x + 5

Step-by-step explanation:

according to factor theroem,

if x-a is a factor then then f (a) = 0

lets try putting x value in equtaion it must come 0 x=5

(-3*5) ^4 + (15*5) - 5+5

=472500

we dont get here answer 0 so it is not factor of it