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4-2.Quadratic Equations and Inequations
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જો $x\, = \,2\, + \,\sqrt 3 $ હોય, તો $x^3 - 7x^2 + 13x - 12$ નું મૂલ્ય કેટલું થાય ?

A

$3$

B

$6$

C

$-9$

D

$9$

Solution

$\,x\, = \,2\, + \,\sqrt 3 \, \Rightarrow \,x\, – \,2\, = \,\sqrt 3 $

$ \Rightarrow \,{x^2}\, + \,\,4\, – \,4x\, = \,3\,\, \Rightarrow \,{x^2}\, – \,4x\, = \, – 1$

$x^2 – 4x + 1 = 0$

હવે આપણે આપેલ સમીકરણને નીચે મુજબ લખી શકાય.

$x^3 – 7x^2 + 13x – 12 = x(x^2 – 4x +1) -3x^2 + 12x – 12$

$= x (x^2 – 4x + 1) – 3(x^2 – 4x + 1) – 9$ 

$= x(0) – 3(0) – 9 = -9$  (હવે $x^2 – 4x + 1 = 0$ કિંમત મૂકતાં )

Standard 11
Mathematics

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