Question

encontre o valor do ■ em cada expressão

(a) (-14)-(-12)=■

(b)(+9)-(■)= -7

(c)(-19)-(■)= -17

(d),■-(-21)=+12​

Answer 1

Resposta:

(a) (-14)-(-12)=■

$- 14 + 12 = - 2$

(b)(+9)-(■)= -7

$9 - x = - 7 \\ 9 - x + 7 = 0 \\ 16 - x = 0 \\ - x = - 16 \times ( - 1) \\ x = 16$

(c)(-19)-(■)= -17

$- 19 - x = - 17 \\ - 19 - x + 17 = 0 \\ - 2 - x = 0 \\ - x = 2 \times ( - 1) \\ x = - 2$

(d),■-(-21)=+12

$x - ( - 21) = 12 \\ x + 21 = 12 \\ x + 21 - 12 = 0 \\ x + 9 = 0 \\ x = - 9$