Đáp án + Giải thích các bước giải:
a)
`F(-1)=|3.(-1)+2|=|(-3)+2|=|-1|=1`
`F(2)=|3.2+2|=|6+2|=|8|=8`
`F(6)=|3.6+2|=|18+2|=|20|=20`
b)
`F(x)=-1`
`<=>|3x+2|=-1`
`|3x+2|\ge0` mà `-1<0`
Vậy `x∈∅`
`F(x)=0`
`<=>|3x+2|=0`
`<=>3x+2=0`
`<=>3x=-2`
`<=>-2/3`
Vậy `x=-2/3`
`F(x)=13`
`<=>|3x+2|=13`
`<=>` \(\left[ \begin{array}{l}3x+2=13\\3x+2=-13\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}3x=11\\3x=-15\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=\dfrac{11}{3}\\x=-5\end{array} \right.\)
Vậy `x∈{11/3;-5}`
