Question

For the following pair of functions, find (f+g)(x) and (f-g)(x).

Answer 1

Given:

The functions are

$f(x)=4x^2+7x-5$

$g(x)=-9x^2+4x-13$

To find:

The functions $(f+g)(x)$ and $(f-g)(x)$.

Solution:

We know that,

$(f+g)(x)=f(x)+g(x)$

$(f+g)(x)=4x^2+7x-5-9x^2+4x-13$

$(f+g)(x)=(4x^2-9x^2)+(7x+4x)+(-5-13)$

$(f+g)(x)=-5x^2+11x-18$

And,

$(f-g)(x)=f(x)-g(x)$

$(f-g)(x)=(4x^2+7x-5)-(-9x^2+4x-13)$

$(f+g)(x)=4x^2+7x-5+9x^2-4x+13$

$(f+g)(x)=(4x^2+9x^2)+(7x-4x)+(-5+13)$

$(f-g)(x)=13x^2+3x+8$

Therefore, the required functions are $(f+g)(x)=-5x^2+11x-18$

and $(f-g)(x)=13x^2+3x+8$.