(x+5)(x-5) multiplied

Short Way: Recognize that this is a special factorization pattern known as "Difference of Squares" (Easy to multiply in your head, once you understand the principal of "Difference of Squares"; google it.)

Long Way: Carry out the multiplication by hand (using polynomial multiplication) and simplify. The set of steps is known as "FOIL" (Still easy, but more steps than the difference-of-squares pattern; tk showed you the steps for FOIL, but you could google "FOIL", too, to learn more.)