Answer:
All real numbers less than or equal to 4.
Step-by-step explanation:
Rearrange it to vertex form:
-(x + 5)(x+1)
= - (x^2 + 6x + 5)
= - [( x + 3)^2 - 9 + 5]
= - (x + 3)*2 + 4
So the vertex is at f(x) = 4 and its a maximum because the coefficient of x^2 is negative.
So the range is all real numbers less than or equal to 4.
