Question

[nguyễn xuân anh kiệt]

giúp mình với
tìm x
9(x-1)-x^3+x^2=0
(2x+1)^2=(x-1)^2
x^2-6x-7=0

Answer 1

[Nguyễn Lê Phước Thịnh]

a: \(9\left(x-1\right)-x^3+x^2=0\)

=>\(9\left(x-1\right)-x^2\left(x-1\right)=0\)

=>\(\left(x-1\right)\left(9-x^2\right)=0\)

=>\(\left[{}\begin{matrix}x-1=0\\9-x^2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x^2=9\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x=1\\x=3\\x=-3\end{matrix}\right.\)

b: \(\left(2x+1\right)^2=\left(x-1\right)^2\)

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

=>(2x+1-x+1)(2x+1+x-1)=0

=>3x(x+2)=0

=>x(x+2)=0

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

c: \(x^2-6x-7=0\)

=>\(x^2-7x+x-7=0\)

=>x(x-7)+(x-7)=0

=>(x-7)(x+1)=0

=>\(\left[{}\begin{matrix}x-7=0\\x+1=0\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x=7\\x=-1\end{matrix}\right.\)

Answer 2

[Nguyễn Nhã Yến]

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