a: \(f\left(-\dfrac{2}{3}\right)=3\cdot\dfrac{-2}{3}-19=-2-19=-21\)
\(f\left(\sqrt{\dfrac{25}{9}}\right)=f\left(\dfrac{5}{3}\right)=3\cdot\dfrac{5}{3}-19=5-19=-14\)
\(f\left(\sqrt{\left(-7\right)^2}\right)=f\left(7\right)=3\cdot7-19=2\)
b: 3x-19=-1/2
=>3x=-1/2+19=18,5
hay x=37/6
3x-19=-5
=>3x=14
=>x=14/3