If 4x- 81 x- then the value of x is

The correct option is nbsp;A. nbsp;± 4.5Given, nbsp;4x=81x⇒ 4x^2=81⇒ x^2=814Taking square root on both the sides we get,⇒√(x^2)=±√(814)⇒ x=±92⇒ x=± 4.5Hen ...

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Standard VII

Mathematics

Integers

If 4x= 81 x...

Question

If $4 x = \frac{81}{x}$ , then the value of $x$ is

- 4.5

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\pm 4.5

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4.5

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Solution

The correct option is A. $\pm 4.5$
Given,
$4 x = \frac{81}{x}$
$\Rightarrow 4 x^{2} = 81$
$\Rightarrow x^{2} = \frac{81}{4}$
Taking square root on both the sides we get,
$\Rightarrow \sqrt{x^{2}} = \pm \sqrt{\frac{81}{4}}$
$\Rightarrow x = \pm \frac{9}{2}$
$\Rightarrow x = \pm 4.5$
Hence, option A is correct.

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If 4x=81x, then the value of x is

The correct option is A. ±4.5Given, 4x=81x⇒4x2=81⇒x2=814Taking square root on both the sides we get,⇒√x2=±√814⇒x=±92⇒x=±4.5Hence, option A is correct.

If $4 x = \frac{81}{x}$ , then the value of $x$ is