Any number raised to power zero = 1.
Note that 0 raised to power 0 is not 1, it is undefined.
Therefore:
(-4x)⁰ = 1
For the second part -4x⁰ = :
x⁰ = 1, -4x⁰ = -4*(1) = -4
This is true on the assumption that x is not equal to zero.
I hope this explains it.
