Processing Math: Done

From Förberedande kurs i matematik 1

The trick is to use the formula for the difference of two squares (a−b)(a+b)=a2−b2 and multiply the top and bottom of the fraction by 3−7  (note the minus sign), since then the new denominator will be (3+7)(3−7)=32−(7)2=9−7=2  (the formula with a=3 and b=7 ), i.e. the root sign is squared away.

The whole calculation is

23+7=23+73−73−7=2(3−7)32−(7)2=223−27=3−7.