Question

Tìm x, cần trk 10h

 \(x^3-3x^2+3x+63=0 \)

Answer 1

     \(x^3-3x^2+3x+63=0\)

\(\Leftrightarrow x^3-3x^2+3x-1+64=0\)

\(\Leftrightarrow\left(x-1\right)^3+64=0\)

\(\Leftrightarrow\left(x-1\right)^3=-64\)

\(\Leftrightarrow x-1=-4\)

\(\Leftrightarrow x=-3\)

Answer 2

x³ +3x²-6x²-18x+21x+63=0

<=>x²(x+3)-6x(x+3)+21(x+3)=0

<=>(x²-6x+21)(x+3)=0

TH1:x²-6x+21=0

      <=>x²-6x+9+12=0

      <=>(x-3)²+12=0

      <=>(x-3)²=-12 (vô lý)

      <=>x thuộc rỗng

TH2:     x+3=0

          <=>x=-3

KL:...........