Question

Se o determinante da Matriz A= [ ] é igual a 5. Calcule o valor de X:
-2 -5
x 5

Answer 1

$\begin{matrix}\begin{vmatrix}-2&-5\\x&5\end{vmatrix}=5\\\\\\(-2\cdot5)-(-5\cdot{x})=5\\\\(-10)-(-5x)=5\\\\-10+5x=5\\\\5x=5+10\\\\5x=15\\\\x=\dfrac{15}{5}\\\\x=3\\\\\\\boxed{S=\{3\}}\end{matrix}$