Câu 2:
a: \(4x^3-4x\)
\(=4x\cdot x^2-4x\cdot1\)
\(=4x\left(x^2-1\right)=4x\cdot\left(x-1\right)\left(x+1\right)\)
c: Sửa đề: \(x^2+y^2-25+2xy\)
Ta có: \(x^2+y^2-25+2xy\)
\(=\left(x^2+2xy+y^2\right)-25\)
\(=\left(x+y\right)^2-25=\left(x+y+5\right)\left(x+y-5\right)\)
d: \(x^2+6x+8\)
\(=x^2+2x+4x+8\)
=x(x+2)+4(x+2)
=(x+2)(x+4)
Câu 3:
a: \(x^2-26x=0\)
=>x(x-26)=0
=>\(\left[\begin{array}{l}x=0\\ x-26=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=0\\ x=26\end{array}\right.\)
b: \(2x^2+3\left(x-1\right)\left(x+1\right)=5x\left(x+1\right)\)
=>\(2x^2+3\left(x^2-1\right)=5x^2+5x\)
=>\(5x^2+5x=2x^2+3x^2-3\)
=>5x=-3
=>\(x=-\frac35\)
