Math, asked by rimmisingh791, 11 months ago

Hey guys


Question:


If x = 1/3-✓8, find the value of x^3-2x^2-7x+5.


Please answer this question and no spams

It's very urgent please solve it correctly.

Answers

Answered by Anonymous
0

Answer:

49+16✓8

Step-by-step explanation:

x = 1/3-✓8

=(3+✓8)/(3-✓8)(3+✓8)

=3+✓8/9-8

x=3+✓8

=================

x²=(3+✓8)^2=9+8+6✓8=17+6✓8

x³= (17+6✓8) (3+✓8)

=51+17✓8+18✓8+6✓8*✓8

=51+35✓8+48

x³=99+35✓8

====================

Now x³-2x²-7x+5

=99+35✓8-2*(17+6✓8)-7(3+✓8)+5

=99+35✓8-34-12✓8-21-7✓8+5

=99-34-21+5+35✓8-19✓8

=49+16✓8


rimmisingh791: Your answer is wrong
Anonymous: 19+1649+16✓8
Anonymous: 49+16✓8=49+16✓8=49+16✓(4*2)=49+16*2✓2=49+32✓2
Anonymous: So answer is same
Anonymous: If you do not like should i get delete the answer
Anonymous: i think you post the question by copy paste for time pass ,bolo
rimmisingh791: Aisa khuch nhi
rimmisingh791: I really not able to understand the question
Anonymous: for me it took @ 15-20 min to answer this question and u simply said WRONG ,this hits me lot.
rimmisingh791: Toh mere khene se Galt ho gya
Answered by Shreyanshijaiswal81
2

x =  \frac{1}{3 -  \sqrt{8} }  =  \frac{1}{3 -  \sqrt{8} }  \times  \frac{(3 +  \sqrt{8}) }{(3 +  \sqrt{8} )}  =  \frac{(3 +  \sqrt{8} }{(3)^{2} - ( \sqrt{8} )^{2}  } \\  =  \frac{(3 +  \sqrt{8} }{9 - 8}  = (3 +  \sqrt{8} )

x = 3 +  \sqrt{8}  =>x - 3 =  \sqrt{8} \\  =>(x - 3)^{2}  =  \sqrt{( {8})^{2} } = 8 \\  => {x}^{2}  + 9 - 6x = 8=> {x}^{2}  - 6x + 1 = 0

 {x}^{3}  -  {2x}^{2}  - 7x + 5 = x( {x}^{2}  - 6x + 1) + 4( {x}^{2} 6x + 1) + 16x + 1 \\  = x \times 0 \times  + 4 \times 0 + 16(3 +  \sqrt{8} ) + 1 \\ =  48 + 16 \sqrt{8}  + 1 = 49 + 32 \sqrt{2}

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