Answer:
N = -1
explanation:
x = N
solving steps:
[tex]\sf f(x)=x^2+2x-15[/tex]
To find symmetry of a quadratic function.
vertex formula : [tex]\sf x=\dfrac{-b}{2a}[/tex]
[tex]a=1,\:b=2[/tex]
[tex]\sf x=\dfrac{-2}{2\cdot \:1}[/tex]
[tex]\sf x = -1[/tex]
Then,
N = -1
