Question

Tìm nghiệm của các đa thức sau:

a) x²+2x

b) x²-3

c) (x-2)²+4

d) x²-3x+2

e) x²+6x+5

Answer 1

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

b) \(x^2-3\Leftrightarrow\left(x-\sqrt{3}\right)\left(x+\sqrt{3}\right)\)

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

c ) \(\left(x-2\right)^2+4=0\Leftrightarrow\left(x-2\right)^2=-4\left(Loại\right)\)

d ) \(x^2-3x+2\Leftrightarrow\left[{}\begin{matrix}x-2=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=1\end{matrix}\right.\)

e ) \(x^2+6x+5\Leftrightarrow\left[{}\begin{matrix}x+1=0\\x+5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=-5\end{matrix}\right.\)