Question

Ache a raiz ou zero das seguintes funções:
A)f(x)=3x+9
B)f(x)=x²-4x+3
C)f(x)=3x
D)f(x)=17-x

Answer 1

Apenas precisamos colocar um zero no lugar do f(x)
Vou fazer as contas pra você:

$A)f(x)=3x+9 \\\\ 0 = 3x + 9\\\\ -3x = 9 \\\\ x = \frac{9}{-3} \\\\ x = -3$




$B)f(x)=x^2-4x+3 \\\\ x^2 - 4x + 3 = 0 \qquad --\ \textgreater \ Bhaskara$



$Retirando~informacoes: \\\\ 1x^2 - 4x + 3 = 0\\ ax^2 + bx + c = 0 \\\\ a = 1 \\ b = -4 \\ c = 3 \\\\ Resolvendo: \\\\ \Delta = b^2 -4.a.c \\ \Delta = (-4)^2 - 4.1.3 \\ \Delta = 16 - 12 \\ \Delta = 4 \\\\ x^+ = \frac{-b \pm \sqrt{\Delta}}{2.a}\\\\ x^+ = \frac{-(-4) + \sqrt{4} }{2.1}\\\\ x^+ = \frac{4 + 2 }{2} \qquad \qquad\qquad x^-= \frac{4 - 2 }{2} \\\\ x^+ = \frac{6 }{2} \qquad \qquad\qquad~~~ x^-= \frac{2}{2} \\\\ x^+ = 3 \qquad \qquad\qquad~~~~ x^- = 1$




$C)f(x)=3x \\\\ 0 = 3x \\\\ \frac{0}{3} = x \\\\ x = 0$




$D)f(x)=17-x \\\\ 0 = 17 - x \\\\ x = 17$

Answer 2

Vamos lá:

f(x) = y = 0

a) f(x) = 3x + 9
3x + 9 = 0
3x = - 9
x = - 9/3
x = - 3

b) f(x) = x^2 - 4x + 3
x^2 - 4x + 3 = 0
x^2 - 4x + 3 + 1 = 0 + 1
x^2 - 4x + 4 = 1
(x - 2)^2 = 1
x - 2 = + ou - 1
x' - 2 = 1
x' = 1 + 2
x' = 3
x" - 2 = - 1
x" = - 1 + 2
x" = 1
x = 3 e x = 1

c) f(x) = 3x
3x = 0
x = 0

d) f(x) = 17 - x
17 - x = 0
- x = - 17
x = 17

Espero ter ajudado.