## Algebra: A Combined Approach (4th Edition)

a) $1$ b) $-1$
a) We use the commutative property of addition to simplify the expression: $\frac{x+4}{4+x} = \frac{x+4}{x+4} = 1$ b) Recognize that the numerator and denominator are opposites. That is, $x-4 = -1(4-x)$. Substituting this into the original fraction, we see: $\frac{-1(4-x)}{4-x} = \frac{-1}{1} = -1$