Question

Tìm x, biết:

a, x³ - 25x = 0

b, 4x² - 4x + 1 - 5(2x - 1) = 0

c, x² - 2x - 8 = 0

d, x² - x = -x² - 2x + 6

Answer 1

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

\(\left(2x-1\right)\left(2x-1-5\right)=0\Rightarrow\left[{}\begin{matrix}2x-1=0\\2x-6=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=3\end{matrix}\right.\)

 

Answer 2

c) \(\Rightarrow x\left(x-4\right)+2\left(x-4\right)=0\Rightarrow\left(x-4\right)\left(x+2\right)=0\)

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

d) \(\Rightarrow2x^2+x-6=0\Rightarrow2x\left(x+2\right)-3\left(x+2\right)=0\)

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

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