Evaluate the limit of the function [(x+5)/(x+2)]^(2x+1) x approaches to + infinite.

1 Answer | Add Yours

giorgiana1976's profile pic

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted on

The limit will go to the base and to the superscript.

The limit of the base is:

lim (x+5)/(x+2) = lim x(1 + 5/x)/x(1 + 2/x) = lim(1 + 5/x)/(1 + 2/x)=1

The limit of superscript is:

lim (2x+1) = +infinite

We notice that we've get an indeterminacy: 1^infinite.

We'll create remarcable limit "e".

We'll add 1 and subtract 1 inside the brackets of the base:

[1 + (x+5)/(x+2) - 1] = [1 + (x+5-x-2)/(x+2)] = [1+ 3/(x+2)]

The remarcable limit is:

lim (1 + 1/x)^x = e, x->infinite

We'll re-write the limit:

lim { [1+ 3/(x+2)]^(x+2)/3}^3(2x+1)/(x+2) = lim { [1+ 3/(x+2)]^(x+2)/3}^ lim 3(2x+1)/(x+2)

lim { [1+ 3/(x+2)]^(x+2)/3} = e

The limit of superscript:

lim 3(2x+1)/(x+2) = lim 3x(2+1/x)/x(1+2/x) =  lim 3(2+1/x)/(1+2/x) = 6/1

The limit of the function, when x approaches to +infinite, is:  lim [(x+5)/(x+2)]^(2x+1) = e^6

We’ve answered 318,994 questions. We can answer yours, too.

Ask a question