Question

Seja f uma função real definida pela lei f(x) =ax-3.se -2 é raiz da função, qual é o valor de f(3)?

Answer 1

Boa tarde Juliana!

Solução!

Sendo -2 a raiz da função,vamos determinar o valor de a,em seguida achar o valor de f(3).

$y=ax-3\\\\\\ Para~~f(x)=0\\\\\ x=-2\\\\\\\ 0=-2a-3\\\\\ 2a=-3\\\\\\ a= -\dfrac{3}{2}\\\\\\\ Logo!\\\\\\ \boxed{f(x)= -\dfrac{3}{2}x-3}$

Vamos determinar f(3)!

$f(x)= -\dfrac{3}{2}x-3}\\\\\\\\ f(3)= -\dfrac{3}{2}.3-3}\\\\\\\\ f(3)= -\dfrac{9}{2}-3}\\\\\\\\ f(3)= \dfrac{-9-6}{2}\\\\\\\\ f(3)= \dfrac{-15}{2}\\\\\\ \boxed{f(3)= -\frac{15}{2} }$

Boa tarde!
Bons estudos!

Answer 2

f(x) = ax - 3

0 = a . (- 2) - 3

0 = - 2a - 3

2a = - 3

a = - 3/2

f(3) = - 3/2 . 3 - 3

f(3) = - 9/2 - 3

f(3) = - (9 + 3)/2

f(3) = - 15/2

Att. YRZ