Answer:
x > -3
Explanation:
The function will be increasing where its derivative is positive.
__
y = x^2 +6x . . . . . given function
y' = 2x +6 . . . . . . . derivative
The derivative is positive for ...
2x +6 > 0
2x > -6
x > -3 . . . . . domain where the function is increasing