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Mathematics

If 9n.32.3n(27)n(3m.2)3=33\dfrac{9^n.3^2.3^n - (27)^n}{(3^m.2)^3} = 3^{-3}.

Show that : m - n = 1.

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Answer

Given,

9n.32.3n(27)n(3m.2)3=33(32)n.32.3n(33)n(3m)3.(2)3=3332n.32.3n33n=33.(3m)3.(2)39.32n+n33n=33.33m.89.33n33n=8.33m333n(91)=8.33m38.33n=8.33(m1)33n=33(m1)3n=3(m1)n=m1mn=1.\Rightarrow \dfrac{9^n.3^2.3^n - (27)^n}{(3^m.2)^3} = 3^{-3} \\[1em] \Rightarrow \dfrac{(3^2)^n.3^2.3^n - (3^3)^n}{(3^m)^3.(2)^3} = 3^{-3} \\[1em] \Rightarrow 3^{2n}.3^2.3^n - 3^{3n} = 3^{-3}.(3^m)^3.(2)^3 \\[1em] \Rightarrow 9.3^{2n + n} - 3^{3n} = 3^{-3}.3^{3m}.8 \\[1em] \Rightarrow 9.3^{3n} - 3^{3n} = 8.3^{3m - 3} \\[1em] \Rightarrow 3^{3n}(9 - 1) = 8.3^{3m - 3} \\[1em] \Rightarrow 8.3^{3n} = 8.3^{3(m - 1)} \\[1em] \Rightarrow 3^{3n} = 3^{3(m - 1)} \\[1em] \Rightarrow 3n = 3(m - 1) \\[1em] \Rightarrow n = m - 1 \\[1em] \Rightarrow m - n = 1.

Hence, proved that m - n = 1.

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