Question

Tìm x, biết:

a ) \(x^2-2x=0\)

b ) \(\left(5-2x\right)^2-16=0\)

c ) \(x\left(x+3\right)-x^2-11=0\)

d ) \(2x^2-7x+3=0\)

e ) \(\left(x+2\right)\left(x^2-2x+4\right)-x\left(x^2+2\right)=0\)

f ) \(x^3-5x^2+10x-8=0\)

Answer 1

\(a,x^2-2x=0\)

\(\Rightarrow x\left(x-2\right)=0\)

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

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

Vậy ...

\(b,\left(5-2x\right)^2-16=0\)

\(\Rightarrow\left(5-2x\right)^2=16\)

\(\Rightarrow\left(5-2x\right)^2=4^2\)

\(\Rightarrow5-2x=\pm4\)

\(\Rightarrow\left[{}\begin{matrix}5-2x=4\\5-2x=-4\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}2x=1\\2x=9\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=\dfrac{2}{9}\end{matrix}\right.\)

Vậy ...

\(c,x\left(x+3\right)-x^2-11=0\)

\(\Rightarrow x^2+3x-x^2-11=0\)

\(\Rightarrow3x-11=0\)

\(\Rightarrow3x=11\)

\(\Rightarrow x=\dfrac{11}{3}\)

Vậy ...