(x+5)(x-5)

This is a difference of 2 squares question.

(x+5)(x-5)=x²-5² = x²-25

FOIL method

FIRST

OUTER

INNER

LAST

(x + 5)(x - 5)

FIRST: (x * x) = x^2

OUTER: (x * -5) = -5x

INNER: (x * 5) = 5x

LAST: (5 * -5) = -25

x^2 - 5x + 5x - 25

The 'x's cancel each other out.

x^2 - 25 is your final answer.