Approximating Square Roots with Linear Approximation

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SUMMARY

The discussion focuses on finding the linear approximation of the function f(x) = sqrt(2x + 2) at the point a = 7 to estimate sqrt(18). The correct linear approximation formula, L(x) = f(a) + f'(a)(x - a), was applied incorrectly by one participant, leading to an erroneous result of 6.75 instead of the actual value of approximately 4.2426. The mistake was identified as failing to solve the equation 2x + 2 = 18 and incorrectly substituting x = 18 into the approximation formula.

PREREQUISITES
  • Understanding of linear approximation and its formula
  • Knowledge of derivatives and how to compute f'(x)
  • Familiarity with the function f(x) = sqrt(2x + 2)
  • Basic algebra skills for solving equations
NEXT STEPS
  • Study the concept of linear approximation in calculus
  • Learn how to compute derivatives, specifically for square root functions
  • Practice solving equations involving square roots and linear functions
  • Explore applications of linear approximation in real-world scenarios
USEFUL FOR

Students studying calculus, particularly those learning about linear approximation and derivatives, as well as educators looking for practical examples to illustrate these concepts.

thushanthan
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Homework Statement



Given f(x)=sqrt(2x+2)

Question : Find the linear approximation of f(x) at a=7 AND use it to approximate sqrt(18).


Homework Equations



L(x)=f(a)+f'(a)(x-a)

The Attempt at a Solution



Using the linear approximation formula I am getting the value 6.75, but when I checked with calculator the value of sqrt(18) is 4.2426...

Did my approximation is wrong?
 
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Yes, you did something wrong. Show us your work. It's kinda hard to tell where you went wrong without that.
 
Thank you :smile:

I didn't solve 2x+2=18. I plugged in x=18 and (x-a) becomes (18-7) = 11.

Now I got it. Thanks.
 

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