Answer: -x+4
Step-by-step explanation: You have to distribute the -1 outiside of the parentheses by multiplying it to the constants inside the parentheses.
So, -1(1) = -1. The new coefficient of x and the first constant of the simplified form is -1
Also, -1(-4) = +4. The new constant after the variable x is 4
Therefore the fully simplified form is
-x + 4