Áp dụng hằng đẳng thức số 4 , ta có :
x3 + 3x2 + 3x + 1 = -1
=> (x + 1)3 = -1
<=> x + 1 = -1
<=> x = -2
\(x^3+3x^2+3x+1=-1\)
\(\Rightarrow\left(x+1\right)^3=-1\)
\(\Leftrightarrow x+1=-1\)
\(\Leftrightarrow x=-1-1\)
\(\Rightarrow x=-2\)
Vậy \(x=-2\)
\(x^3+3x^2+3x+1=-1\)
\(\Rightarrow x^3+x^2+2x^2+2x+x+1=-1\)
\(\Rightarrow\left(x^3+x^2\right)+\left(2x^2+2x\right)+\left(x+1\right)=-1\)
\(\Rightarrow x^2.\left(x+1\right)+2x.\left(x+1\right)+\left(x+1\right)=-1\)
\(\Rightarrow\left(x+1\right).\left(x^2+2x+1\right)=-1\)
\(\Rightarrow\left(x+1\right).\left(x^2+x+x+1\right)=-1\)
\(\Rightarrow\left(x+1\right)^3=-1\)
\(\Rightarrow x+1=-1\Rightarrow x=-2\)
Vậy \(x=-2\)
Chúc bạn học tốt!!!
