Question

determine o termo deconhecido$\left[\begin{array}{ccc}-2&1&x\\1&2&4\\3&-1&-2\end{array}\right] =-7$

Answer 1

Utilize a regra de Sarrus

$-2.2.(-2)+1.4.3+x.1.(-1)-3.2.x-1.1.(-2)-(-2).4.(-1)=-7\newline 8+12-x-6x+2-8=-7\newline -7x=-7-14\newline x= \frac{-21}{-7}=3$


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