Question

VALENDO 20 PONTOS!!!
Determine o valor de x na equacao $\left[\begin{array}{ccc}x&x+4\\5&7&\\&&\end{array}\right]$ = 0
POR FAVOR COM CÁLCULOS


a) x = 5

b) x = -2

c) x = 8

d) x = 10

e) x =4,5

Answer 1

A = ( a b )

      ( c d ), então det(A) = ad - bc

D = ( x x+4 )

      ( 5    7  ), então

7x - 5x - 20 = 0

2x = 20

x = 20/2

x = 10

Resposta: d) x = 10

Answer 2

Explicação passo-a-passo:

$\sf \Big|\begin{array}{cc} \sf x & \sf x+4 \\ \sf 5 & \sf 7 \end{array}\Big|=0$

$\sf x\cdot7-5\cdot(x+4)=0$

$\sf 7x-5x-20=0$

$\sf 2x-20=0$

$\sf 2x=20$

$\sf x=\dfrac{20}{2}$

$\sf \red{x=10}$

Letra D