Question

Preciso disso URGENTE!

1- Seja f uma função real definida pela lei f(x)= ax - 3. Se -2 é a raiz da função, qual o valor de f(4)?


2- Realize o estudo da função:
a) f(x) = 3x + 6

b) f(x) = -x -5

Answer 1

$1)\\\\f(x)=ax-3\\f(-2)=0\\f(-2)=a\cdot(-2)-3\\f(-2)=-2a-3\\-2a-3=0\\-2a=3\\\\\\a= -\dfrac{3}{2}\\\\\\f(x)= -\dfrac{3}{2}\cdot{x}-3\\\\\\f(4)=- \dfrac{3}{2}\cdot4-3\\\\\\f(4)=-6-3\\\\\\\boxed{f(4)=-9}$

$2)\\\\a\_\ \ f(x)=3x+6\\\\3x+6=0\\3x=-6\\x=-2\\\\Como\ o\ coeficiente\ angular\ \'e\ maior\ que\ 0\, essa\, reta\ \'e\ crescente$

$-2\ \'e\ a\ raiz\ dessa\ fun\c{c}\~ao$

$b\_\ \ f(x)=-x-5\\\\-x-5=0\\-x=5\\x=-5\\\\Como\ o\ coeficiente\ angular\ \'e\ menor\ que\ 0,\ essa\ reta\ \'e\ decrescente$

$-5\ \'e\ a\ raiz\ dessa\ fun\c{c}\~ao$

Answer 2

F (x ) = Ax - 3
F ( - 2) = - 2a - 3 =0
- 2a = 3
a = - 3 / 2
F (4 ) = - 3 / 2 * 4 - 3
F ( 4 ) = - 6 - 3
F ( 4 ) = - 9

2) 3x - 6 = 0
3x = 6
x = 3
y = 0 > x = 3
y> 0 x > 3
Y < 0 x <3


- x - 5 = 0
x = - 5
y = 0 ,. x = -5
y > 0 x < - 5
y < 0. x > - 5