Question

Dada as funções: f(x)= 3x²-x+5 e g(x)= -2x+9, determine o valor de f(x)= g(x)

Answer 1

$3 x^{2} -x+5=-2x+9$

$3 x^{2} +x-4=0$

Δ = $1-4.3.(-4)=1+48=49$

$x_{1} = \frac{-1+ \sqrt{49} }{2.3} =\frac{-1+ 7 }{6}= \frac{6}{6} =1$
ou
$x_{2} = \frac{-1- \sqrt{49} }{2.3} =\frac{-1- 7 }{6}= \frac{-8}{6} =- \frac{4}{3}$

Para x = 1 ⇒ $f(x)=g(x)$$=-2.1+9=9-2=7$

Para x = $- \frac{4}{3}$ ⇒ $f(x)=g(x)$$=-2. (-\frac{4}{3} )+9= \frac{8}{3} +9 =\frac{8+27}{3} = \frac{35}{3}$