78 , 79 fast pls

Please find below the solution to the asked query:

78 )   We have : $\frac{\sqrt{1296}}{x} = \frac{x}{2.25}$ , So

$$\begin{gathered} \frac{\sqrt{2 \times 2 \times 2 \times 2 \times 3 \times 3 \times 3 \times 3}}{x} = \frac{x}{2.25} \\ \Rightarrow \frac{ 2 \times 2 \times 3 \times 3}{x} = \frac{x}{2.25} \\ \Rightarrow \frac{36}{x} = \frac{x}{2.25} \\ \Rightarrow x^2 = 36 \times 2.25 \\ \Rightarrow x^2 = 81 \\ \Rightarrow x^2 = 9^2 \\ \mathbf{\Rightarrow }\mathit{x}\mathbf{ }\mathbf{=}\mathbf{ }\mathbf{9}\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{(}\mathbf{ }\mathbf{Ans}\mathbf{ }\mathbf{)} \end{gathered}$$
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