The answer is C)
You can do this by several ways. The more direct is to realize that (x-5)(x+5) is a factorization of a difference of squares.
Also, you can apply the distributive propierty:
[tex]\begin{gathered} x\cdot x=x^2 \\ x\cdot5=5x \\ -5\cdot x=-5x \\ (-5)\cdot5=-25 \end{gathered}[/tex]
Now, you add everithing up:
[tex]\begin{gathered} (x-5)(x+5)=x^2+5x-5x-25=x^2-25 \\ \end{gathered}[/tex]
And then you get the answer C)
