First I’m not sure if it was supposed to be 6k4 or 6k^4 but I did it 6k^4
In order to solve for f(-4) we know what the value is for K
So in the formula f(k)=6k^4 +2k^3 -6 we would replace K with (-4)
f(-4)= 6(-4)^4+2(-4)^3-6
Then start solving the exponents first
(-4)^4=256
(-4)^3=-64
f(-4)= 6(256)+2(-64)-6
= 1536-128-6
=1408-6
f(-4)= 1402