Question

Answer 1

Áp dụng Vi-ét có: `{(x_1+x_2=[-b]/a=3/2),(x_1.x_2=c/a=1/2):}`

Có:`B=20(x_1+x_2)-22x_1.x_2`

`<=>B=20. 3/2-22 . 1/2`

`<=>B=19`

Answer 2

\(\Delta=\left(-3\right)^2-4.2=9-8=1>0\)

--> pt luôn có 2 nghiệm phân biệt

Theo hệ thức Vi-ét, ta có:\(\left\{{}\begin{matrix}x_1+x_2=\dfrac{3}{2}\\x_1x_2=\dfrac{1}{2}\end{matrix}\right.\)

\(B=20\left(x_1+x_2\right)-22x_1x_2\)

\(B=20.\dfrac{3}{2}-22.\dfrac{1}{2}\)

\(B=30-11\)

\(B=19\)