a) \(x^2-y^2+5x+5y\)
\(=\left(x^2-y^2\right)+\left(5x+5y\right)\)
\(=\left(x-y\right).\left(x+y\right)+5.\left(x+y\right)\)
\(=\left(x+y\right).\left(x-y+5\right)\)
b) \(3x^2+3y^2-6xy-12\)
\(=3.\left(x^2+y^2-2xy-4\right)\)
\(=3.\left[\left(x^2+y^2-2xy\right)-4\right]\)
\(=3.\left(x-y\right)^2-4\)
\(=3.\left(x-y\right)^2-2^2\)
\(=3.\left(x-y-2\right).\left(x-y+2\right)\)
Chúc bạn học tốt!