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## Homework Statement

lim x->-inf 2*x-sqrt(4*x^2+x+1)

## Homework Equations

## The Attempt at a Solution

For positive inf, i got -inf(not sure)

but negative inf, i got -1/4

http://www.wolframalpha.com/input/?i=lim+2*x-sqrt%284*x^2%2Bx%2B1%29

but wolfram have switch the answer, which is right, so i don't know which part i am wrong

lim X->-inf

2*x-sqrt(4*x^2+x+1)

2*x-sqrt(4*x^2+x+1)*((2*x+sqrt(4*x^2+x+1))/(2*x+sqrt(4*x^2+x+1))

(4x^2+4x^2-x-1)/(2*x-sqrt(4*x^2+x+1))

-x-1/(2*x-sqrt(4*x^2+x+1))

-x/(2x-sqrt(4x^2) X<0 sqrt(4x^2) =|2x|=-2x

-x/(2x-(-2x))=-1/4

lim x->+inf

-x/(2x-sqrt(4x^2) X>0 sqrt(4x^2) =|2x|=2x

-x/0= -inf?

Thanks