What is P(-4) given that P(x) = 2x to the fourth power - 3x to the third power + 5x to the 2nd power - 1?

Let's first write that out as an equation.

P(x) = 2x^4 -3x^3 +5x^2 -1.
P(-4) = 2*256 -3*(-64) +5*16 -1
= 783