\(\left|x\right|=3\) \(\Rightarrow\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\)
`@` Với `x=3`
\(A.B=\left(-2x^2+3x+5\right).\left(x^2-x+3\right)\)
\(=\left(-2.3^2+3.3+5\right).\left(3^2-3+3\right)\)
\(=-4.9\)
`=-36`
`@`Với `x=-3`
\(A.B=\left(-2x^2+3x+5\right).\left(x^2-x+3\right)\)
\(=\left[-2.\left(-3\right)^2+3.\left(-3\right)+5\right].\left[\left(-3\right)^2-\left(-3\right)+3\right]\)
\(=-22.15\)
\(=-330\)
ta thay |x|=3
TH1 : x=3
A =-2.32+3.3+5
A=-4
B=32-3+3
B=9
A.B=9.-4=-36
TH2 : x=-3
A =-2.(-3)2+3.-3+5
A=14
B=(-3)2-(-3)+3
B=15
A.B=14.15=210
