Approximating Square Roots with Linear Approximation

In summary, for the given function f(x) = sqrt(2x+2), the linear approximation at a=7 is found using the formula L(x) = f(a) + f'(a)(x-a). When this formula is used to approximate sqrt(18), the value obtained is 6.75. However, this is incorrect as the correct value for sqrt(18) is 4.2426. To find the correct linear approximation, the equation 2x+2=18 must be solved, and x=8 is obtained. When x=8 is substituted into the linear approximation formula, the correct value of 4.2426 is obtained.
  • #1
thushanthan
32
0

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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  • #2
Yes, you did something wrong. Show us your work. It's kinda hard to tell where you went wrong without that.
 
  • #3
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.
 

1. What is linear approximation?

Linear approximation is a mathematical method for approximating the value of a function near a specific point. It involves using the tangent line at the point to approximate the value of the function.

2. How is linear approximation used in real life?

Linear approximation is used in various fields, such as physics, engineering, and economics, to estimate the behavior of a system or process near a specific point. It is also used in financial modeling and forecasting.

3. What is the difference between linear approximation and linear interpolation?

While both methods involve estimating the value of a function, linear approximation uses the tangent line at a specific point, while linear interpolation uses a line connecting two known data points to estimate the value at an unknown point.

4. What are the limitations of linear approximation?

Linear approximation is only accurate near the chosen point and becomes less accurate as the distance from the point increases. It also assumes that the function is continuous and differentiable at the point.

5. How can I calculate linear approximation?

To calculate linear approximation, you will need the value of the function at the chosen point and the slope of the tangent line at that point. You can then use the formula y = f(a) + f'(a)(x-a) to find the approximate value of the function at a nearby point x.

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