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Find the value of xxx if x128=162x\frac{x}{\sqrt{128}} = \frac{\sqrt{162}}{x}128​x​=x162​​​
Question

Find the value of xx if x128=162x\frac{x}{\sqrt{128}} = \frac{\sqrt{162}}{x}

A.

144

B.

196

C.

14

D.

12

Correct option is D

Given: 

x128=162x\frac{x}{\sqrt{128}} = \frac{\sqrt{162}}{x} 

Solution:

Multiply both sides of the equation by x128 x \cdot \sqrt{128}  to eliminate the fractions:

x2=128162x^2 = \sqrt{128} \cdot \sqrt{162} 

Simplify the Square Roots: 

128\sqrt{128}  = 642=642=82 \sqrt{64 \cdot 2} = \sqrt{64} \cdot \sqrt{2} = 8\sqrt{2}  

162=812=812=92 \sqrt{162} = \sqrt{81 \cdot 2} = \sqrt{81} \cdot \sqrt{2} = 9\sqrt{2}  

Now, 

x2=(82)(92)x^2 = (8\sqrt{2}) \cdot (9\sqrt{2}) 

x2=8922x^2 = 8 \cdot 9 \cdot \sqrt{2} \cdot \sqrt{2} 

x2=892=144x^2 = 8 \cdot 9 \cdot 2 = 144 

x=144=12x = \sqrt{144} = 12 

The value of x is 12

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