calc

Quote:

X-1 * X = X^2-X .. why not X^2-1 ???

as you've written it

X - 1 * X = X - X = 0

you probably meant

(X-1) * X

so you much multiply each term inside the parens by the X, thus

(X-1) * X = X*X - 1*X = X ² - X