Answer:
-4x + 5x = 1x.
We can add like terms and simplify to answer this question,
-4x and 5x both have the variable and the exponent in common so we can combine their terms. When adding a negative to a positive it becomes subtraction. Since 5 is bigger we are subtracting 4 from 5.
We can add the coefficients:

Keeping the variable:
