\(a,f\left(3\right)=3.3-8=9-8=1\\ f\left(-2\right)=3\left(-2\right)-8=-6-8=-14\)
\(b,y=3x-8\\ \Rightarrow1=3x-8\\ \Rightarrow9=3x\\ \Rightarrow x=3\)
- khi f(x)=3 ta có:
=3.3-8
=9-8
=1
- khi f(x)=-2 ta có:
=3.(-2)-8
=-6-8
=-14
b, khi y=1 ta có:
1=3x-8
1+8=3x
9=3x
x=3
Lời giải:
a. Ta có:
$f(3)=3.3-8=1$
$f(-2)=3(-2)-8=-14$
b.
$y=f(x)=3x-8=1$
$\Rightarrow 3x=9$
$\Rightarrow x=3$