Question

1) \(27+\left(x-3\right).\left(x^2+3x+9\right)=-x\)

2) \(-4\left(x+2\right)-7\left(2x-1\right)+9\left(4-3x\right)=30\)

3) \(x^2-4x+4=0\)

4) \(\left(x-1\right).\left(x^2+x+1\right)-x.\left(x+2\right).\left(x-2\right)=5\)

Tìm x giúp mk vs nha mai mk đi hk rùi

Answer 1

1)

\(27+(x-3)(x^2+3x+9)=-x\)

\(\Leftrightarrow 27+(x^3-3^3)=-x\)

\(\Leftrightarrow x^3=-x\)

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

\(\Rightarrow \left[\begin{matrix} x=0\\ x^2+1=0(vl)\end{matrix}\right.\)

Vậy $x=0$

2)

\(-4(x+2)-7(2x-1)+9(4-3x)=30\)

\(\Leftrightarrow -4x-8-14x+7+36-27x=30\)

\(\Leftrightarrow -45x+35=30\Leftrightarrow -45x=-5\)

\(\Rightarrow x=\frac{-5}{-45}=\frac{1}{9}\)

Answer 2

3)

\(x^2-4x+4=0\)

\(\Leftrightarrow x^2-2.2x+2^2=0\)

\(\Leftrightarrow (x-2)^2=0\Rightarrow x-2=0\Rightarrow x=2\)

4)

\((x-1)(x^2+x+1)-x(x+2)(x-2)=5\)

\(\Leftrightarrow (x^3-1^3)-x[(x+2)(x-2)]=5\)

\(\Leftrightarrow x^3-1-x(x^2-2^2)=5\)

\(\Leftrightarrow x^3-1-x^3+4x=5\)

\(\Leftrightarrow 4x-1=5\Rightarrow 4x=6\Rightarrow x=\frac{6}{4}=\frac{3}{2}\)