Question

x³+3x²+3x=-7/8

Mong mng giúp ạ!

Answer 1

\(x^3+3x^2+3x=-\dfrac{7}{8}\\ x^3+3x^2+3x+1=1-\dfrac{7}{8}\\ \left(x+1\right)^3=\dfrac{1}{8}\\ x+1=\dfrac{1}{2}\\ x=-\dfrac{1}{2}\)

Answer 2

Ta có: \(x^3+3x^2+3x=\dfrac{-7}{8}\)

\(\Leftrightarrow\left(x^3+3x^2+3x+1\right)=\dfrac{1}{8}\)

\(\Leftrightarrow\left(x+1\right)^3=\left(\dfrac{1}{2}\right)^3\)

\(\Leftrightarrow x+1=\dfrac{1}{2}\)

hay \(x=-\dfrac{1}{2}\)

Vậy: \(S=\left\{-\dfrac{1}{2}\right\}\)