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Assuming $f(x)=ax^3+bx^2+cx+d$

show that $\lim_{x\rightarrow\infty}f(x)$ and $\lim_{x\rightarrow -\infty}f(x)$ exists, find the limits.$a,b,c,d\in\mathbb{R}$

Well, I think the limits exists in extended real line and their values are simply $+\infty$ and $-\infty$. If I am missing something please help.

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    Unless all the coefficients besides d are 0, the limits should be $\pm\infty$. If a is 0 and b is not, you get the same limits for both ends. If a is not 0 or if a and b are both 0 , you get limits with opposite sign, with the concrete results depending on the sign of a or c respectively. If every coefficent but d is zero, the limits on both end simply are d2012-11-30

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