Answer:
x^4- x^3- 4x^2-3 
Explanation:
Given 
f(x)= x^4- x^2+9 
And 
g(x)= x^(3 )+ 3x^2+12 
We have to find 
(f-g)(x)= ? 
The operations on functions are as easy as the operations on numbers or polynomials. 
We have to subtract the functions to find the above mentioned operation. 
=(f-g)(x)=f(x)-g(x) 
(f-g)(x)=[x^4- x^2+9]-[x^(3 )+ 3x^2+12] 
The minus will change the signs of function g. 
= x^4- x^2+9- x^(3 )- 3x^2-12 
= x^4- x^3- x^2- 3x^2+9-12 
=x^4- x^3- 4x^2-3