Question

Calcule o valor das expressões:

a) $\frac{1}{ \sqrt{2} } - \frac{3}{ \sqrt{8} }$

b) $\sqrt{9+3 \sqrt{3} } . \sqrt{9-3 \sqrt{3} }$

Answer 1

a) 1/√2 - 3/√8 = ...
√8 = √(4x2) = 2√2
1/√2 = 1.√2 / √2.√2 = √2/2
3/2√2 = (3.√2) / (2√2.√2) = 3√2/(2.2) = 3√2/4

√2/2 - 3√2/4 = ...
mmc 2 e 4 = 4
(4:2.√2)/4 - 3√2/4 = 
2√2/4 - 3√2/4 = -√2/4

b) √(9+3√3).(9-3√3) = √(9)²-(3√3)² = √(81-9.3) = √(81-27) = √54 = √(9x6) = 3√6