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anonymous
 4 years ago
prove that
x^8 x^7 + x^2 x +15 has no real root
anonymous
 4 years ago
prove that x^8 x^7 + x^2 x +15 has no real root

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anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0for \(x\le0\) its obvious that \(x^8 x^7 + x^2 x +15 >0\) u just prove for \(x>0\) : \(x^8 x^7 + x^2 x +15 >0\)

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0and does descartes' theorem help a great deal ? according to that,,it should have max 4 +ve roots..

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0no need to descartes...

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0well just show that \(x^8 x^7 + x^2 x +15>0\) for every real number

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0descartes helps a lot lol

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0for x>1 ,, x^8 > x^7 and x^2 >x so f(x) > 0 for x>1 for 0<x<1 , x> x^2 > x^7 > x^8 we then have 15  (fraction + fraction) ,,which is obviously >0 so f(x) is always >0 am i right ?

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0ohh..thank you @mukushla your little hint only helped me a lot :)
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