Processing Math: Done

From Förberedande kurs i matematik 1

If we use the rule for squaring (a−b)2=a2−2ab+b2 with a=x and b=7, we obtain directly that

(x−7)2=x2−2x7+72=x2−14x+49.

An alternative is to write the square as (x−7)(x−7) and then multiply the brackets in two steps

(x−7)(x−7)=(x−7)x−(x−7)7=xx−7x−(x7−77)=x2−7x−(7x−49)=x2−7x−7x+49=x2−(7+7)x+49=x2−14x+49.

In the line that has been marked with an asterisk, we have removed the bracket and at the same time changed signs on all terms inside the bracket.