Question

Giải phương trình:

a) 2x³ - 50x = 0

b) 5x² - 4(x² - 2x + 1) - 5 = 0

Answer 1

a/ \(\Leftrightarrow2x\left(x^2-25\right)=0\)

\(\Leftrightarrow2x\left(x-5\right)\left(x+5\right)=0\)

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

b/ \(\Leftrightarrow5\left(x^2-1\right)-4\left(x-1\right)^2=0\)

\(\Leftrightarrow\left(x-1\right)\left(5x+5\right)-4\left(x-1\right)^2=0\)

\(\Leftrightarrow\left(x-1\right)\left(5x+5-4x+4\right)=0\)

\(\Leftrightarrow\left(x-1\right)\left(x+9\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=1\\x=-9\end{matrix}\right.\)