Question

3. Dada a função f(x) = - x 2 + x + 6, determine as raízes da função. a) S={ 2, 3} b) S = { -1, 4} c) S = { 0,2} d) S = {-2,3}

Answer 1

Resposta:

D

Explicação passo-a-passo:

$\sf -x^2+x+6=0$

$\sf \Delta=1^2-4\cdot(-1)\cdot6$

$\sf \Delta=1+24$

$\sf \Delta=25$

$\sf x=\dfrac{-1\pm\sqrt{25}}{2\cdot(-1)}=\dfrac{-1\pm5}{-2}$

$\sf x'=\dfrac{-1+5}{-2}~\longrightarrow~x'=\dfrac{4}{-2}~\longrightarrow~x'=-2$

$\sf x"=\dfrac{-1-5}{-2}~\longrightarrow~x"=\dfrac{-6}{-2}~\longrightarrow~x"=3$

$\sf S=\{-2,3\}$

Letra D