find the largest interval in

find the largest interval in which x lies satisfying

x^{12}-x^{9}+x^{4}-x+1>0

4 Answers

1708
man111 singh ·

$\textbf{Let $\mathbf{f(x) = x^{12}-x^9+x^4-x+1}$}\\\\ \textbf{Let $\mathbf{x\geq 1,}$ Then $\mathbf{f(x)=x^9(x^3-1)+x(x^3-1)+1>0}$ }\\\\ \textbf{Now for $\mathbf{x<1}$, Then $\mathbf{f(x)=x^{12}+x^4(1-x^5)+(1-x)}>0$ }\\\\

$\textbf{So Largest Interval for which $\mathbf{f(x)>0}$ is $\mathbf{x<1}$ }$\\\\ \boxed{\boxed{\mathbf{x\in\left(-\infty,1\right)}}}$

62
Lokesh Verma ·

So the final answer should be R....

1
paresh baruah ·

yes ans is R. plz help

62
Lokesh Verma ·

arrey the answer is given by jagdish in #2...

he has proved it for both the cases... when x>1 and when x<1

so effectively he has proved it for all real values of x..

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