esce 22 giusto?
esce 22 giusto?
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$\bigg\{\begin{array}{rl}3x & +7y =11\\x&+5y = 1 \\ \end{array}$
determinante → $D=\bigg|\begin{array}{rl}3 & +7\\1&+5 \\ \end{array}\bigg|$ $= 3·5-1·7 = 15-7 = 8$
determinante di $x$ → $Dx=\bigg|\begin{array}{rl}11 & +7\\1&+5 \\ \end{array}\bigg|$ $= 11·5-1·7 = 55-7 = 48$
determinante di $y$ → $Dy=\bigg|\begin{array}{rl}3 & +11\\1&+1 \\ \end{array}\bigg|$ $= 3·1-1·11 = 3-11 = -8$
per cui:
$x= \dfrac{Dx}{D}= \dfrac{48}{8} = 6$;
$y= \dfrac{Dy}{D}= \dfrac{-8}{8} = -1$.