Question

alguem pode me ajudar ???????


Estude a variação de sinal (y > 0 ou y < 0) das seguintes funções do 1º grau:

a) f(x) = x + 5

b) f(x) = -3x + 9

c) f(x) = 2 – 3x

d) f(x) = -2x + 10​

Answer 1

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$\tt{a)}~\sf{f(x)=x+5}\\\sf{f(x)=0\implies x=-\dfrac{5}{1}=-5}\\\sf{f(x)\textgreater0\implies x\textgreater-5}\\\sf{f(x)\textless0\implies x\textless-5}$

$\tt{b)}~\sf{f(x)=-3x+9}\\\sf{f(x)=0\implies x=-\dfrac{9}{-3}=3}\\\sf{f(x)\textgreater0\implies x\textless3}\\\sf{f(x)\textless0\implies x\textgreater3}$

$\tt{c)}~\sf{f(x)=2-3x}\\\sf{f(x)=0\implies x=-\dfrac{2}{-3}=\dfrac{2}{3}}\\\sf{f(x)\textgreater0\implies x\textless\dfrac{2}{3}}\\\sf{f(x)\textless0\implies x\textgreater\dfrac{2}{3}}$

$\tt{d)}~\sf{f(x)=-2x+10}\\\sf{f(x)=0\implies x=-\dfrac{10}{-2}=5}\\\sf{f(x)\textgreater0\implies x\textless5}\\\sf{f(x)\textless0\implies x\textgreater5}$