Bài 4:
a: \(\Leftrightarrow5x\left(x-1\right)+\left(x-1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(5x+1\right)=0\)
hay \(x\in\left\{1;-\dfrac{1}{5}\right\}\)
b: \(\Leftrightarrow x^2-6x+9-x^2-6x-9=24\)
=>-12x=24
hay x=-2
c: \(\Leftrightarrow x\left(x-2\right)\left(x+2\right)=0\)
hay \(x\in\left\{0;2;-2\right\}\)
d: \(\Leftrightarrow A=\dfrac{x\left(x-5\right)\left(x+5\right)}{x-5}=x\left(x+5\right)\)
e: \(\Leftrightarrow A=\dfrac{\left(x-y\right)\left(4-x\right)}{y-x}=x-4\)