Đa thức \(-27y^3-9y^2-y-\dfrac{1}{27}\) được thu gọn là
\(\left(-3y+\dfrac{1}{3}\right)^3\).\(\left(-3y-\dfrac{1}{3}\right)^3\).\(\left(3y-\dfrac{1}{3}\right)^3\).\(\left(3y+\dfrac{1}{3}\right)^2\).Hướng dẫn giải:Ta có: \(-27y^3-9y^2-y-\dfrac{1}{27}\)\(=-\left(27y^3+9y^2+y+\dfrac{1}{27}\right)\)
\(=-\left(3y+\dfrac{1}{3}\right)^3=\left(-1\right)^3\left(3y+\dfrac{1}{3}\right)^3=\left(-3y-\dfrac{1}{3}\right)^3\).
