\(B=2\cdot\left(\dfrac{1}{2}\right)^3-\dfrac{1}{3}\cdot\dfrac{1}{4}-\left|\dfrac{1}{2}-\dfrac{1}{4}\right|\)
\(=2\cdot\dfrac{1}{8}-\dfrac{1}{12}-\dfrac{1}{2}\)
\(=\dfrac{1}{4}-\dfrac{1}{12}-\dfrac{1}{2}\)
\(=\dfrac{3}{12}-\dfrac{1}{12}-\dfrac{6}{12}\)
\(=\dfrac{-1}{3}\)
\(B=2x^3-\dfrac{1}{3}x^2-\left|x-\dfrac{1}{4}\right|\)
Thay \(x=\dfrac{1}{2}\) vào biểu thức ta có:
\(B=2\left(\dfrac{1}{2}\right)^3-\dfrac{1}{3}.\left(\dfrac{1}{2}\right)^2-\left|\dfrac{1}{2}-\dfrac{1}{4}\right|\)
\(=2.\dfrac{1}{8}-\dfrac{1}{3}.\dfrac{1}{4}-\dfrac{1}{2}\)
\(=\dfrac{1}{4}-\dfrac{1}{12}-\dfrac{1}{2}\)
\(=-\dfrac{1}{3}\)
