06.08.2013 Views

Applied Calculus Math 215 - University of Hawaii

Applied Calculus Math 215 - University of Hawaii

Applied Calculus Math 215 - University of Hawaii

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

18 CHAPTER 1. SOME BACKGROUND MATERIAL<br />

Let us do a higher degree example:<br />

Example 1.11. Let p(x) =x 4 −2x 3 +5x 2 −x+3 and x0 =2. Finda<br />

line l(x) and a constant A, such that |p(x) − l(x)| ≤A(x−x0) 2 for all x<br />

in the interval I =(1,3). (Note that the open interval I contains the point<br />

x0 =2.)<br />

Expanding p(x) inpowers<strong>of</strong>(x−2) we find<br />

p(x) =(x−2) 4 +6(x−2) 3 + 17(x − 2) 2 + 27(x − 2) + 21.<br />

Set l(x) = 27(x − 2) + 21. Then<br />

|p(x) − l(x)| = 4 3 2<br />

(x − 2) +6(x−2) + 17(x − 2) <br />

= <br />

2<br />

(x − 2) +6(x−2) + 17 2<br />

(x − 2)<br />

≤ (1 + 6 + 17)(x − 2) 2<br />

≤ 24(x − 2) 2 .<br />

In the calculation we used the triangle inequality ((5.9) in Section 5.2 to get<br />

the first inequality. If x ∈ (1, 3), then |x − 2| < 1and|x−2| k

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!