Question

Giúp mình mấy câu gạch chân màu đỏ với

Answer 1

Answer 2

e) Ta có: \(x^2-4x+5=0\)

\(\Leftrightarrow\left(x-2\right)^2+1=0\)(Vô lý)

f) Ta có: \(x\left(x-2\right)+x-2=0\)

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

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

g) Ta có: 5x(x-3)-x+3=0

\(\Leftrightarrow\left(x-3\right)\left(5x-1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=\dfrac{1}{5}\end{matrix}\right.\)

h) Ta có: \(x^3-\dfrac{1}{4}x=0\)

\(\Leftrightarrow x\left(x-\dfrac{1}{2}\right)\left(x+\dfrac{1}{2}\right)=0\)

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

i) Ta có: \(x^2\left(x-3\right)-4x+12=0\)

\(\Leftrightarrow\left(x-3\right)\left(x-2\right)\left(x+2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=2\\x=-2\end{matrix}\right.\)

Answer 3

e) Cho \(đa\) \(thức\) \(x^2-4x+5=0\)

\(Ta\) \(có\) \(x^2-4+5=0\)

\(x^2-4=0+5\)

\(x^2-4=5\)

\(x^2=5+4\)

\(x^2=9\)

\(\Rightarrow x=\pm3\)

\(Vậy\) \(nghiệm\) \(của\) \(đa\) \(thức\) \(x^2-4x+5\) \(là \) \(0\)