Question

Considere a função do 1°grau F(x)=-3x+2.Determine os valores de x para que se tenha:
a)F(x)=4
b)F(x)=20
c)F(x)=1/2
d)F(x)=12

Answer 1

a) $f(x)=4$

$-3x+2=4~\longrightarrow~-3x=4-2~\longrightarrow~-3x=2$

$x=\dfrac{2}{-3}~\longrightarrow~\boxed{x=-\dfrac{2}{3}}$


b) $f(x)=20$

$-3x+2=20~\longrightarrow~-3x=20-2~\longrightarrow~-3x=18$

$x=\dfrac{18}{-3}~\longrightarrow~\boxed{x=-6}$


c) $f(x)=\dfrac{1}{2}$

$-3x+2=\dfrac{1}{2}~\longrightarrow~2\cdot(-3x+2)=1$

$-6x+4=1~\longrightarrow~-6x=1-4~\longrightarrow~-6x=-3$

$x=\dfrac{-3}{-6}~\longrightarrow~\boxed{x=\dfrac{1}{2}}$


d) $f(x)=12$

$-3x+2=12~~\longrightarrow~-3x=12-2~\longrightarrow~-3x=10$

$x=\dfrac{10}{-3}~\longrightarrow~\boxed{x=-\dfrac{10}{3}}$