Find the values of each of the following correct to three places of decimals, it being given that
$\sqrt{2}=1.414, \sqrt{3}=1.732, \sqrt{5}=2.236, \sqrt{6}=2.4495, \sqrt{10}=3.162$
(i) $\frac{3-\sqrt{5}}{3+2 \sqrt{5}}$
(ii) $\frac{1+\sqrt{2}}{3-2 \sqrt{2}}$
(i) $\frac{3-\sqrt{5}}{3+2 \sqrt{5}}$
Rationalizing the denominator by multiplying both numerator and denominator with the rationalizing factor
$3-2 \sqrt{5}$
$=\frac{(3-\sqrt{5})(3-2 \sqrt{5})}{(3+2 \sqrt{5})(3+2 \sqrt{5})}$
Since, $(a+b)(a-b)=\left(a^{2}-b^{2}\right)$
$=\frac{(3-\sqrt{5})(3-2 \sqrt{5})}{9-20}$
$=\frac{(9-6 \sqrt{5}-3 \sqrt{5}+10)}{-11}$
$=\frac{(19-9 \sqrt{5})}{-11}$
$=\frac{(9 \sqrt{5}-19)}{11}$
$=\frac{(9(2.236)-19)}{11}$
$=\frac{(20.124-19)}{11}$
$=\frac{1.124}{11}$
$=0.102$
(ii) $\frac{1+\sqrt{2}}{3-2 \sqrt{2}}$
Rationalizing the denominator by multiplying both numerator and denominator with the rationalizing factor
$3+2 \sqrt{2}$
$=\frac{(1+\sqrt{2})(3+2 \sqrt{2})}{(3-2 \sqrt{2})(3+2 \sqrt{2})}$
As we know, $(a+b)(a-b)=\left(a^{2}-b^{2}\right)$
$=\frac{(1+\sqrt{2})(3+2 \sqrt{2})}{9-8}$
$=3+2 \sqrt{2}+3 \sqrt{2}+4$
$=7+5 \sqrt{2}$
$=7+7.07=14.07$