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Mathematics

If 3+232=a+b2\dfrac{3 + \sqrt{2}}{3 - \sqrt{2}} = a + b\sqrt{2}, find the values of 'a' and 'b'.

Rational Irrational Nos

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Answer

Given,

Equation : 3+232=a+b2\dfrac{3 + \sqrt{2}}{3 - \sqrt{2}} = a + b\sqrt{2}

Rationalizing L.H.S. of the above equation :

3+232×3+23+2(3+2)2(3)2(2)2(3)2+(2)2+2×3×2929+2+62711+627117+627\Rightarrow \dfrac{3 + \sqrt{2}}{3 - \sqrt{2}} \times \dfrac{3 + \sqrt{2}}{3 + \sqrt{2}} \\[1em] \Rightarrow \dfrac{(3 + \sqrt{2})^2}{(3)^2 - (\sqrt{2})^2} \\[1em] \Rightarrow \dfrac{(3)^2 + (\sqrt{2})^2 + 2 \times 3 \times \sqrt{2}}{9 - 2} \\[1em] \Rightarrow \dfrac{9 + 2 + 6\sqrt{2}}{7} \\[1em] \Rightarrow \dfrac{11 + 6\sqrt{2}}{7} \\[1em] \Rightarrow \dfrac{11}{7} + \dfrac{6\sqrt{2}}{7}

Comparing 117+672 with a+b2\dfrac{11}{7} + \dfrac{6}{7}\sqrt{2} \text{ with } a + b\sqrt{2}, we get :

a=117 and b=67.a = \dfrac{11}{7} \text{ and } b = \dfrac{6}{7}.

Hence, a=117 and b=67a = \dfrac{11}{7} \text{ and } b = \dfrac{6}{7}.

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