\(Q=\left(x+3\right)^2+\left(x+3\right)\left(x-3\right)-2\left(x+2\right)\left(x-4\right)\)
\(Q=x^2+6x+9+x^2-9-2\left(x^2-4x+2x-8\right)\)
\(Q=x^2+6x+9+x^2-9-2\left(x^2-2x-8\right)\)
\(Q=x^2+6x+9+x^2-9-2x^2-4x+16\)
\(Q=2x+16\)
Khi \(x=\dfrac{1}{2}\), ta có :
\(2.\dfrac{1}{2}+16=17\)
Vậy