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The value of a^3-2a^2-7a+5, if a=1/(2-3^2)

Guest Mar 7, 2017
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 #1
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a^3-2a^2-7a+5, if a=1/(2-3^2)   →   a  =  -1/7........so.....

 

(-1/7)^3 - 2(-1/7)^2 - 7(-1/7) + 5   =

 

-1/343 - 2/49 + 1 + 5

 

-1/343 - 14/343 + 6

 

-15/343 + 6 

 

-15/343 + 2058/343  =

 

2043 / 343

 

 

cool cool cool

CPhill  Mar 7, 2017
 #2
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The value of a^3-2a^2-7a+5, if a=1/(2-  root(3))  ,,,the answer is 2,, give me the explanation!! 

Guest Mar 7, 2017
 #3
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The value of a^3-2a^2-7a+5, if a=1/(2-3^2)

 

By saying a=1/ (2 - 3^2) =1/(2 - 9) =1/ - 7. If by 3^2, you mean the"square root of 3", you don't write it 3^2 BUT as "sqrt(3)". Now let us see what we get:

1/(2 - sqrt(3)) = 1/(2 - 1.732....) =1/0.268 =3.7313.... Substitute in your equation:

(3.7313)^3 - (2x3.7313^2) - (7x3.7313) + 5 =

51.949..     -    27.845...     -     26.119   + 5 = 3 - The answer would be 3 NOT 2, if you didn't round off. 

Guest Mar 7, 2017

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