Question

Resolva as equações a seguir

A)$\left[\begin{array}{ccc}4x&2x&\\9&5&\\&&\end{array}\right] =8$

B) $\left[\begin{array}{ccc}-3&x&2\\-4&x&x\\-2&1&3\end{array}\right] =0$


Ajuda por favor 

Answer 1

a) $\left[\begin{array}{ccc}4x&2x\\9&5\end{array}\right] =8$

2x*9=18x       4x*5=20x  

det = 20x - 18x
 8 = 2x
 x= 8/2
 x = 4 

b) $\left[\begin{array}{ccc}-3&x&2\\-4&x&x\\-2&1&3\end{array}\right] = 0$

|-3 x 2| -3 x
|-4 x x| -4 x
|-2 1 3|-2 1

diag. principal: -9x - 2x² - 8
diag. secundaria: -4x - 3x - 12x = -19x

det = - 9x - 2x² - 8 - (-19x)
0 = -2x² + 10x - 8
2x² - 10x + 8 = 0  (÷2)
x² - 5x + 4 = 0

Δ= (-5)²-4.1.4
Δ= 25 - 16
Δ= 9

x' = -b+√Δ          x'' = -b-√Δ
      ---------                ---------
          2a                      2a

x' = 5+3             x'' = 5-3
     --------                 ------
         2                        2

x' = 8/2              x'' = 2/2
x' = 4                 x'' = 1