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
0
1 + 1 a
1
x (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
1
1 = 1 mx
1
1 + 1 c
y
2
1 = 1 mx
2
1 + 1 c
() () () ()−=−+−+−=−+
=
∑
xxxxxxx
i
i
234234
2
4
x
n
xxxx
x
xx x
n
n
21 1135 35
0
3
11234
1
23 4
−−
=
= + + + =++ +
∑∑
ix x x x x x x x
i
i
=× +× +× +× =+ +
=
∑
0123 23
01 2 3 23
0
3
2.5 Polynomials 41
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−c/m
x
1
x
2
(x
1
,y
1
)
(x
2
,y
2
)
y
2
−y
1
x
2
−x
1
y
2
y
1
y
x
c
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Figure 2.6