Algebra
posted by Lea .
Simplify (x7)( x+7)

You can multiply these binomials like any other.
x times x and x times 7
then 7 times x and  7 times 7
x^2 + 7x  7x 49
x^2 49
Or you can recognize this pair as a sum and difference which always multiplies to be the difference of two squares.
(a+b)(ab) = a^2 b^2