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Salut! As avea nevoie sa ma rezolvati cu o problema.
Aria triunghiului de varfuri A(1,2), B(2,-3),C(0,-4) este ?
A. 3/2
B. 3
C. 1/2
D.4
Desigur cu explicatie.


Răspuns :

[tex]\it S=\dfrac{1}{2}\cdot|\Delta|\\ \\ \\ \Delta =\ \ \begin{vmatrix}1&2&1\\2&-3&1\\0&-4&1 \end{vmatrix} \stackrel{\ell_2-2\ell_1}{\Longrightarrow}\ \Delta=\ \begin{vmatrix}1&2&1\\0&-7&-1\\0&-4&1 \end{vmatrix}=-7-4=-11\\ \\ \\ S=\dfrac{1}{2}\cdot|-11|=\dfrac{11}{2}=5,5\ u,\ a.[/tex]