Answer:
Option B
Step-by-step explanation:
For increasing function in the interval (a, b),
"If we draw a tangent at any point on the graph in the given interval (a, b), slope of the tangent drawn will be positive"
Given function is,
[tex]f(x)=\frac{1}{2}x^2+5x+6[/tex]
In the interval (-∞, -5),
Graph is moving downwards therefore, tangents drawn at any point will have a negative slope and the function will decrease in this interval.
In the interval (-5, ∞),
In the given interval any tangent drawn at any point will have a positive slope and the function will be increasing.
Therefore, interval in which the function is increasing → (-5, ∞)
Option B is the answer.