Got confused by this limit at infinity problem I do know that the answer is -9/2 though I don't get much on how to get that answer I know how to do it with fractions though.

so lim x - +infinity (sqrt(x^4-9x^2)-x^2)

Question

Got confused by this limit at infinity problem I do know that the answer is -9/2 though I don't get much on how to get that answer I know how to do it with fractions though.

so lim x -> +infinity (sqrt(x^4-9x^2)-x^2)

anonymous · Answer

$$\lim_{x \rightarrow +\infty} (\sqrt[4]{x^4-9x^2} - x^2)$$ better visual lol

mathmale · Answer

I'd suggest that you multiply (and then divide) this expression by its conjugate.  That way you'll end up with a more familiar form:  a fraction.  Try it, please.

anonymous · Answer

i got $$\frac{ -9x^2}{ \sqrt[4]{x^4-9x^2}+x^2 } $$ i am going the right way? XD

anonymous · Answer

I probably need some sleep now if ever you come back could you please tell the next steps I'll get back to it in the morning lol.

mathmale · Answer

Think of what would happen to this expression if x were now to increase without bound.   Note that x^4 is >>>x^2 in this scenario.  does a limit seem any more tangible now?