Only real coefficients are discussed here; the case of complex coefficients is shown
in Section 8.4 to involve no new principles.
EXAMPLE 2.13Write out in full:
(1)
(2)
(3)
0 Exercises 36–39
Degree n 1 = 11 : linear function
f(x) 1 = 1 a
01 + 1 a
1x (2.11)
This is the simplest type of function, and is better known in the form
y 1 = 1 mx 1 + 1 c (2.12)
The graph of the function is a straight line. It has slope m, and intercepts the vertical
y-axis (whenx 1 = 10 ) at the pointy 1 = 1 c, as shown in Figure 2.6.
If we take any two points on the line, with coordinates (x
1,y
1) and (x
2,y
2), then
y
11 = 1 mx
11 + 1 c
y
21 = 1 mx
21 + 1 c
() () () ()−=−+−+−=−+
=∑
xxxxxxx
ii23423424x
n
xxxx
x
xx x
nn21 1135 350311234
1
23 4
−−== + + + =++ +
∑∑
ix x x x x x x x
ii=× +× +× +× =+ +
=∑
0123 23
01 2 3 23032.5 Polynomials 41
......................................................................................................................................................................................................................................................................................−c/m
x
1x
2(x
1,y
1)
(x
2,y
2)
y
2−y
1x
2
−x
1
y
2y
1y
x
c
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Figure 2.6