Which polynomial is a difference of two squares?
x2 + 25
x2 − 25
x2 − 10
x2 + 10

Difference of two numbers means one number subtracted from the other number. x^2 is the square of x. 25 = 5^2, and 5^2 is the square of 5. So this is the difference of x^2 and 5^2, the difference of two squares.
x^2 - 25 = (x-5)(x+5)
answer= x^2-25.