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160 Chapter 3. Maps Between Spaces<br />

then this correspondence preserves the operations, for instance this addition<br />

� 1 2 � + � 3 4 � = � 4 6 � ←→<br />

and this scalar multiplication.<br />

5 · � 1 2 � = � 5 10 � ←→ 5 ·<br />

More generally stated, under the correspondence<br />

both operations are preserved:<br />

and<br />

� �<br />

a0 a1 ←→<br />

� �<br />

1<br />

+<br />

2<br />

� �<br />

a0<br />

� � � � � �<br />

a0 a1 + b0 b1 = a0 + b0 a1 + b1 ←→<br />

a1<br />

r · � � � �<br />

a0 a1 = ra0 ra1 ←→ r ·<br />

(all of the variables are real numbers).<br />

� �<br />

1<br />

=<br />

2<br />

� �<br />

3<br />

=<br />

4<br />

� �<br />

5<br />

10<br />

� �<br />

4<br />

6<br />

� � � �<br />

a0 b0<br />

+ =<br />

a1<br />

b1<br />

� � � �<br />

a0 ra0<br />

=<br />

a1 ra1<br />

� a0 + b0<br />

a1 + b1<br />

1.2 Example Another two spaces we can think of as “the same” are P2, the<br />

space of quadratic polynomials, and R 3 . A natural correspondence is this.<br />

a0 + a1x + a2x 2 ←→<br />

⎛<br />

⎝<br />

a0<br />

a1<br />

a2<br />

⎞<br />

⎠ (e.g., 1 + 2x +3x2 ⎛ ⎞<br />

1<br />

←→ ⎝2⎠)<br />

3<br />

The structure is preserved: corresponding elements add in a corresponding way<br />

a0 + a1x + a2x 2<br />

+ b0 + b1x + b2x 2<br />

(a0 + b0)+(a1 + b1)x +(a2 + b2)x 2<br />

and scalar multiplication corresponds also.<br />

←→<br />

⎛<br />

⎝ a0<br />

⎞ ⎛<br />

⎠ + ⎝ b0<br />

⎞ ⎛<br />

⎠ =<br />

r · (a0 + a1x + a2x 2 )=(ra0)+(ra1)x +(ra2)x 2 ←→ r ·<br />

a1<br />

a2<br />

b1<br />

b2<br />

�<br />

⎝ a0 + b0<br />

a1 + b1<br />

a2 + b2<br />

⎞<br />

⎠<br />

⎛<br />

⎝ a0<br />

⎞ ⎛<br />

a1⎠<br />

= ⎝<br />

a2<br />

ra0<br />

⎞<br />

ra1⎠<br />

ra2

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