Question

$$\frac{ 3 }{ 7+3 \sqrt{ 2 } } \times \frac{ 7-3 \sqrt{ 2 } }{ 7-3 \sqrt{ 2 } }$$

Answer

(3*(7-3*sqrt(2)))/31

Solution


Rationalize the denominator: \(\frac{3}{7+3\sqrt{2}} \cdot \frac{7-3\sqrt{2}}{7-3\sqrt{2}}=\frac{21-9\sqrt{2}}{{7}^{2}-{(3\sqrt{2})}^{2}}\).
\[\frac{21-9\sqrt{2}}{{7}^{2}-{(3\sqrt{2})}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Factor out the common term \(3\).
\[\frac{3(7-3\sqrt{2})}{{7}^{2}-{(3\sqrt{2})}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Simplify  \({7}^{2}\)  to  \(49\).
\[\frac{3(7-3\sqrt{2})}{49-{(3\sqrt{2})}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Rationalize the denominator: \(\frac{3(7-3\sqrt{2})}{49-{(3\sqrt{2})}^{2}} \cdot \frac{49+{(3\sqrt{2})}^{2}}{49+{(3\sqrt{2})}^{2}}=\frac{1029+378-441\sqrt{2}-162\sqrt{2}}{{49}^{2}-{({(3\sqrt{2})}^{2})}^{2}}\).
\[\frac{1029+378-441\sqrt{2}-162\sqrt{2}}{{49}^{2}-{({(3\sqrt{2})}^{2})}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Factor out the common term \(3\).
\[\frac{3(343+126-147\sqrt{2}-54\sqrt{2})}{{49}^{2}-{({(3\sqrt{2})}^{2})}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Collect like terms.
\[\frac{3((343+126)+(-147\sqrt{2}-54\sqrt{2}))}{{49}^{2}-{({(3\sqrt{2})}^{2})}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Simplify  \((343+126)+(-147\sqrt{2}-54\sqrt{2})\)  to  \(469-201\sqrt{2}\).
\[\frac{3(469-201\sqrt{2})}{{49}^{2}-{({(3\sqrt{2})}^{2})}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Factor out the common term \(67\).
\[\frac{3\times 67(7-3\sqrt{2})}{{49}^{2}-{({(3\sqrt{2})}^{2})}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Simplify  \(3\times 67(7-3\sqrt{2})\)  to  \(201(7-3\sqrt{2})\).
\[\frac{201(7-3\sqrt{2})}{{49}^{2}-{({(3\sqrt{2})}^{2})}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Simplify  \({49}^{2}\)  to  \(2401\).
\[\frac{201(7-3\sqrt{2})}{2401-{({(3\sqrt{2})}^{2})}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Use Power Rule: \({({x}^{a})}^{b}={x}^{ab}\).
\[\frac{201(7-3\sqrt{2})}{2401-{(3\sqrt{2})}^{4}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Rewrite \(2401-{(3\sqrt{2})}^{4}\) in the form \({a}^{2}-{b}^{2}\), where \(a=49\) and \(b=18\).
\[\frac{201(7-3\sqrt{2})}{{49}^{2}-{18}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Simplify  \({49}^{2}\)  to  \(2401\).
\[\frac{201(7-3\sqrt{2})}{2401-{18}^{2}}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Simplify  \({18}^{2}\)  to  \(324\).
\[\frac{201(7-3\sqrt{2})}{2401-324}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Simplify  \(2401-324\)  to  \(2077\).
\[\frac{201(7-3\sqrt{2})}{2077}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Simplify  \(\frac{201(7-3\sqrt{2})}{2077}\)  to  \(\frac{3(7-3\sqrt{2})}{31}\).
\[\frac{3(7-3\sqrt{2})}{31}\times \frac{7-3\sqrt{2}}{7-3\sqrt{2}}\]
Cancel \(7-3\sqrt{2}\).
\[\frac{3}{31}(7-3\sqrt{2})\]
Simplify.
\[\frac{3(7-3\sqrt{2})}{31}\]

Decimal Form: 0.266841