a ) \(x+5x^2=0\)
\(\Leftrightarrow x\left(1+5x\right)=0\)
\(\Leftrightarrow\left[\begin{array}{nghiempt}x=0\\1+5x=0\end{array}\right.\)
\(\Leftrightarrow\left[\begin{array}{nghiempt}x=0\\5x=1\end{array}\right.\Leftrightarrow\left[\begin{array}{nghiempt}x=0\\x=\frac{1}{5}\end{array}\right.\)
b ) \(x+1=\left(x+1\right)^2\)
\(\Leftrightarrow\left(x+1\right)-\left(x+1\right)^2=0\)
\(\Leftrightarrow-\left(x-1\right)=0\)
\(\Leftrightarrow x-1=0\)
\(\Leftrightarrow x=1\)
c ) \(x^3+x=0\)
\(\Leftrightarrow x\left(x^2+1\right)=0\)
\(\Leftrightarrow x=0\) ( Vì \(x^2+1>0\) )
a) x + 5x2 = 0
=>x(1+5x)=0
=>x=0 hoặc 1+5x=0
=>x=0 hoặc x=-1/5
b) x + 1 = ( x + 1 )2
=>(x+1)-(x+1)2=0
=>(x+1)[1-(x+1)]=0
=>-x(x+1)=0
=>-x=0 hoặc x+1=0
=>x=0 hoặc x=-1
c) x3 + x = 0
=>x(x2+1)=0
=>x=0 hoặc x2+1=0
Ta thấy: \(x^2\ge0\Rightarrow x^2+1\ge1>0\) -->vô nghiệm
=>x=0
