SOLUTION: For the function ​f(x)=x^2+2x-15 solve the following. ​f(x) less than or equal to 0

Solve the equation

    x^2 + 2x - 15 = 0


by factoring

    (x+5)*(x-3) = 0.


The roots are  x= - 5  and  x= 3.



Since the leading coefficient at x^2 is positive ( it is 1 ),  the parabola is open up.


So, it is negative between the roots and positive outside.



Thus the answer to the problem's question is this set  -5 <= x <= 3,

or, in the interval form, the set  [-5,3].