How can I solve a one-sided limit without using l'Hopital's rule?

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SUMMARY

The limit as x approaches -1 from the right for the expression lim _{x-> -1+} (sqrt(x^2-3x)-2)/|x+1| can be solved without using l'Hôpital's rule by rationalizing the numerator. Since x is greater than -1, the absolute value |x+1| simplifies to x+1. By multiplying the expression by the conjugate of the numerator over itself, the limit can be evaluated directly, yielding a result of -5/4.

PREREQUISITES
  • Understanding of limits in calculus
  • Familiarity with rationalizing expressions
  • Knowledge of absolute value functions
  • Basic algebraic manipulation skills
NEXT STEPS
  • Study the process of rationalizing numerators in limits
  • Learn about evaluating limits without l'Hôpital's rule
  • Explore the properties of absolute value in calculus
  • Practice solving one-sided limits with various functions
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Students studying calculus, particularly those learning about limits and seeking alternative methods to l'Hôpital's rule. This discussion is beneficial for anyone looking to strengthen their algebraic manipulation skills in the context of calculus.

squirrelschaser
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Homework Statement

Find the ## lim _{x-> -1+} sqrt(x^2-3x)-2/|x+1| ##

Homework Equations

The Attempt at a Solution



I can only solve it using l'hopital rule and would like to know the steps of solving it without using it.

## lim _{x->-1+} (2x-3)/|1|= -5/4 ##
 
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squirrelschaser said:

Homework Statement

Find the ## lim _{x-> -1+} sqrt(x^2-3x)-2/|x+1| ##

Homework Equations

The Attempt at a Solution



I can only solve it using l'hopital rule and would like to know the steps of solving it without using it.

## lim _{x->-1+} (2x-3)/|1|= -5/4 ##
Multiply the expression by 1 in the form of the conjugate of the numerator over itself. The |x + 1| factor in the denominator can be replaced by x + 1, since x is to the right of -1, so x + 1 > 0. If the limit had been as x approaches -1 from the left you have to replace |x + 1| by -(x + 1).
 
squirrelschaser said:

Homework Statement

Find the ## lim _{x-> -1+} sqrt(x^2-3x)-2/|x+1| ##

Homework Equations

The Attempt at a Solution



I can only solve it using l'hopital rule and would like to know the steps of solving it without using it.

## lim _{x->-1+} (2x-3)/|1|= -5/4 ##

I suppose you mean$$
\lim_{x\to -1^+}\frac{\sqrt{x^2-3x}-2}{|x+1|}$$which is not what you wrote. Anyway since ##x>-1## you can write ##|x+1|=x+1##. Try rationalizing the numerator and see if you can get it then.

[Edit] Mark44 must type faster than I do.
 
Last edited:
I'm dumb. Much thanks.
 
No, you are careless- that, at least, is curable!
 

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