Processing Math: Done

From Förberedande kurs i matematik 1

If we consider the rule

(x−a)2=x2−2ax+a2

and move a2 over to the left-hand side, we obtain the formula

(x−a)2−a2=x2−2ax.

With the help of this formula, we can rewrite (complete the square of) a mixed expression x2−2ax to a obtain a quadratic expression, (x−a)2−a2.

The expression x2−2x corresponds to a=1 in the formula above and thus

x2−2x=(x−1)2−1.