Question

  

Answer 1

c: \(x^3-3x^2+x-3=0\)

=>\(\left(x^3-3x^2\right)+\left(x-3\right)=0\)

=>\(x^2\left(x-3\right)+\left(x-3\right)=0\)

=>\(\left(x-3\right)\left(x^2+1\right)=0\)

mà \(x^2+1>=1>0\forall x\)

nên x-3=0

=>x=3

d: \(\left(3x+5\right)^2=\left(x-7\right)^2\)

=>\(\left(3x+5\right)^2-\left(x-7\right)^2=0\)

=>\(\left(3x+5+x-7\right)\left(3x+5-x+7\right)=0\)

=>\(\left(4x-2\right)\left(2x+12\right)=0\)

=>\(\left[{}\begin{matrix}4x-2=0\\2x+12=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=-6\end{matrix}\right.\)