Given:
The functions are
[tex]f(x)=-5x^2+4x-9[/tex]
[tex]g(x)=8x^2-3x-4[/tex]
To find:
The value of (f+g)(x).
Solution:
We know that,
[tex](f+g)(x)=f(x)+g(x)[/tex]
Putting the given functions, we get
[tex](f+g)(x)=-5x^2+4x-9+8x^2-3x-4[/tex]
On combining like terms, we get
[tex](f+g)(x)=(-5x^2+8x^2)+(4x-3x)+(-9-4)[/tex]
[tex](f+g)(x)=3x^2+x-13[/tex]
Therefore, the required function is [tex](f+g)(x)=3x^2+x-13[/tex].