Question

32. Quando x = -2/3,o valor numérico da expressão
3x2^2- x - 2 é:
a) o
b) 1
c)-1
d)1/3
e) -2/3

Answer 1

Resposta:

$\boxed{\mathtt{A}}$

Explicação passo-a-passo:

$\\ \displaystyle \mathsf{3x^2 - x - 2 = } \\ \mathsf{3x^2 - (3x - 2x) - 2 =} \\ \mathsf{(3x^2 - 3x) + (2x - 2) =} \\ \mathsf{3x \cdot (x - 1) + 2 \cdot (x - 1) =} \\ \mathsf{(x - 1) \cdot (3x + 2) =}$

Substituindo,

$\\ \displaystyle \mathsf{\left ( - \frac{2}{3} - 1 \right ) \cdot \left ( 3 \cdot \frac{- 2}{3} + 2 \right ) =} \\\\ \mathsf{\left ( - \frac{2}{3} - \frac{3}{3} \right ) \cdot (- 2 + 2) =} \\\\ \mathsf{- \frac{5}{3} \cdot 0 =} \\\\ \boxed{\boxed{\mathsf{0}}}$