Question

Tính giá trị biểu thức sau: A=\(\dfrac{2x^3+3x-1}{3x-2}\)với | x - 1 | =\(\dfrac{2}{3}\)

Answer 1

Lời giải:

\(|x-1|=\frac{2}{3}\Rightarrow \left[\begin{matrix} x-1=\frac{2}{3}\\ x-1=\frac{-2}{3}\end{matrix}\right.\Rightarrow \left[\begin{matrix} x=\frac{5}{3}\\ x=\frac{1}{3}\end{matrix}\right.\)

Nếu \(x=\frac{5}{3}\) thì \(A=\frac{2(\frac{5}{3})^3+3.\frac{5}{3}-1}{3.\frac{5}{3}-2}=\frac{358}{81}\)

Nếu \(x=\frac{1}{3}\) thì \(A=\frac{2(\frac{1}{3})^3+3.\frac{1}{3}-1}{3.\frac{1}{3}-2}=\frac{-2}{27}\)