Math, asked by poonambhaisare828, 2 days ago

prove that 1/2 -√5/3 is irrational number​

Answers

Answered by vaibhav4674
0

Answer:

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Answered by manmeetmaan20
1

Answer:

If possible let x be a rational number equal to 1/2 -√5/3

x =  \frac{1}{2}  -  \frac{ \sqrt{5} }{3}  \\ squaring \: both \: sides \\  {x}^{2}  =    (\frac{1}{2}  -  \frac{ \sqrt{5} }{3} ) {}^{2}  \\  {x}^{2}  = ( \frac{1}{2} ) {}^{2}  + ( \frac{ \sqrt{5} }{3} ) {}^{2}  - 2( \frac{1}{2} )( \frac{ \sqrt{5} }{3} )  \\  {x}^{2}  =  \frac{1}{4}  +  \ \frac{5}{9}  -  \frac{ \sqrt{5} }{3}  \\  {x}^{2}  -  \frac{1}{4}  -  \frac{5}{9}  =  \frac{ -  \sqrt{5} }{3}   \\  {x}^{2}  -  \frac{21}{36}  =  \frac{ -  \sqrt{5} }{3}  \\ 3( {x}^{2}  -  \frac{21}{36})  =  -  \sqrt{5}  \\  {3x}^{2}  -  \frac{21}{12}  =   -  \sqrt{5}  \\

Now‚

is a rational no.

-21/36 is a rational no.

3x² is also a rational no.

-21/12 is also an irrational no.

-√5 is a rational no.

But,

-√5 is an irrational no.

Thus , we arrive at a contradiction . So , our supposition that 1/2 -√5/3 is a rational no. is wrong Hence 1/2 -√5/3 is an irrational no.

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