Weazl
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Evaluate the limit as x approaches 1 of the quotient of the square root of the quantity x squared plus 24 minus 5 and the quantity x minus 1.
                    sqr root(x^2 + 24) - 5
Lim as x->1   -----------------------------
                                  x - 1
Can you please explain how I would prove this?

Respuesta :

       sqr root(x^2 + 24) - 5
Lim as x->1   -----------------------------
                                  x - 1
when you will put x=1 in denominator that time it will become 0.
that whole part will become infinity
lim x--->1 
[tex] \sqrt{ (x^{2} +24)-5} [/tex]/x-1

In numerator put x=1 u will get
lim x--->1 √(1)²+24/1-1
lim x--->1 √25/0

so that the resulting fraction approaches ∞
ok, so if you tried to evaluate it, we would get something/0, which is undefined
not helpful

hmm
the next step would be to try and factor something out
well, I don't see what to factor out
the next try would be to use l'hopital's rule

take derivitive of top and bottom
derivitive of top is [tex] \frac{x}{ \sqrt{x^2+24} } [/tex]
derivitive of bottom is 1
so we get[tex] \frac{\frac{x}{ \sqrt{x^2+24} }}{1} =\frac{x}{ \sqrt{x^2+24} }[/tex]
if we input 1 for x we get
 
[tex] \frac{1}{ \sqrt{1^2+24} } [/tex]=[tex] \frac{1}{ \sqrt{1+24} } [/tex]=[tex] \frac{1}{ \sqrt{25} } [/tex]=[tex] \frac{1}{5} [/tex]
we know it can't be [tex] \frac{-1}{5} [/tex] because if we evaluated it at x=0 and x=2, we see that it is above 0


the as x->1, [tex] \frac{ \sqrt{x^2+24} -5}{x-1} [/tex]=1/5
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