When I expand (2x + 7)(x - 1), I get 2x^2 + 5x - 7.
I can use my calculator to help me check if my answer is correct.
For instance, if x = 2,
(2x + 7)(x - 1) = 11
2x^2 + 5x - 7 = 11
That means I have done my expansion correctly.
I can safely say, I can do this with any value of x and for any given expression.
Do you agree? Justify your argument with example(s).