√(9-√43)² +√(6-√43)²= |9 -√43| + |6-√43 | = 9-√43-6+√43 =3
√(9-√43)² - √(6-√43)²=| 9 -√43| - |6-√43| = 9 -√43 + 6 -√43 = 15-2√43
√(9-√43)² + √(6+√43)²= 9 -√43 + 6+√43 = 15
8/3√2=(8*√2) /(3√2*√2)= 8√2 /6
4 /(√13 -3)= (4*(√13 +3)) / ((√13 -3)*(√13 -3))= (4*(√13 +3)) / (√13² -3²) =
= (4*(√13 +3)) / (13 - 9) = (4*(√13 +3)) / 4 = √13 +3