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Web skærmformat. - Aarhus Universitet

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V. Matricer – 2. Lineære afbildninger 387<br />

For en m × n-matrix A defineres en afbildning<br />

ved<br />

Eksempel <br />

u1<br />

↦→<br />

u2<br />

1 2<br />

3 4<br />

R n → R m<br />

u ↦→ Au<br />

u1<br />

u2<br />

<br />

u1 + 2u2<br />

=<br />

3u1 + 4u2<br />

2.5. Matrix til lineær afbildning ☞ [LA] 3 Lineære funktioner<br />

Sætning 4<br />

Funktionen f : R n → R m<br />

f(u) = Au<br />

defineret ved en m × n-matrix A er lineœr<br />

Bevis<br />

f(u + v) = f(u) + f(v)<br />

f(αu) = αf(u)<br />

A(u + v) = Au + Av, A(αu) = αAu<br />

Fra de simple regneregler for matrix multiplikation.

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