x？ +4x-5≠0

Get:

X≦-5 and x≠ 1

The domain of the function is

(-∞,-5)∪(-5, 1)∪( 1,+∞)

Let g(x)=x? +4x-5

The symmetry axis is x=-2,

When x

When x >-2, g(x) increases monotonically.

According to the monotonicity of the composite function,

The increasing interval of the original function is

(-∞,-5)∪(-5,-2)

That is, the monotone decreasing interval of g(x) on the definition domain.