a. x(x - 3) + x2 + 5 = 0
\(\Leftrightarrow x^2-3x+x^2+5=0\)
\(\Leftrightarrow2x^2-3x+5=0\)
\(\Leftrightarrow2\left(x-\frac{3}{4}\right)^2+\frac{31}{8}>0\)
Vô nghiệm
b)x2-6x=0
\(\Rightarrow x\left(x-6\right)=0\)
\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x-6=0\end{array}\right.\)
\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x=6\end{array}\right.\)
c)2x3+5x2-12x=0
\(\Leftrightarrow x\left(2x^2+5x-12\right)=0\)
\(\Leftrightarrow x\left(2x^2-3x+8x-12\right)=0\)
\(\Leftrightarrow x\left[x\left(2x-3\right)+4\left(2x-3\right)\right]=0\)
\(\Leftrightarrow x\left(x+4\right)\left(2x-3\right)=0\)
\(\Leftrightarrow\left[\begin{array}{nghiempt}x=0\\x+4=0\\2x-3=0\end{array}\right.\)
\(\Leftrightarrow\left[\begin{array}{nghiempt}x=0\\x=-4\\x=\frac{3}{2}\end{array}\right.\)
a) x^2 - 3x + x^2 +5 =0
=> -3x + 5 = 0
=> -3x = -5
=> x= 5/3
b)x^2 - 6x = 0
x( x - 6 ) = 0
=> x =0
hoặc x-6 =0 => x = 6
vậy x =0 hoặc x =6
=> ...........
