I just need step by step explanation please that would help me out very much.

Given
[tex]\begin{gathered} f(x)=2x+1 \\ g(x)=x^2-7 \end{gathered}[/tex]To find
[tex](f+g)(x)[/tex]Step 1
[tex]Add\text{ f(x) to }g(x)\text{ to obtain (f+g)(x)}[/tex][tex]\begin{gathered} f(x)\text{ + g(x)=(f+g)(x)} \\ (f+g)(x)=(2x+1)+(x^2-7) \\ (f+g)(x)=x^2+2x-7+1 \\ (f+g)(x)=x^2+2x-6 \end{gathered}[/tex]Hence, the answer is option D