x2+x-12
=x2+4x-3x-12
=(x2-3x)(4x-12)
=x(x-3)4(x-3)
=(x+4)(x-3)
x2 + x - 12
=x\(^2\) + 4x - 3x - 12
=x(x+4)-3(x+4)
=(x-3)(x+4)
\(x^2+x-12\)
\(=x^2+4x-3x-12\)
\(=\left(x^2+4x\right)-\left(3x-12\right)\)
\(=x.\left(x+4\right)-3.\left(x+4\right)\)
\(=\left(x+4\right).\left(x-3\right)\)
Chúc bạn học tốt!