\(12y-9x^2+36-3x^2y\)
\(=\left(36-9x^2\right)-\left(3x^2y-12y\right)\)
\(=-9\left(x^2-4\right)-3y\left(x^2-4\right)\)
\(=\left(-3\right)\left(x-2\right)\left(x+2\right)\left(3+y\right)\)
\(12y-9x^2+36-3x^2y\)
\(=\left(12y-3x^2y\right)-\left(9x^2-36\right)\)
\(=3y\left(4-x^2\right)-9\left(x^2-4\right)\)
\(=3y\left(4-x^2\right)+9\left(4-x^2\right)\)
\(=\left(3y+9\right)\left(4-x^2\right)\)
\(=3\left(y+3\right)\left[\left(2^2\right)-x^2\right]\)
\(=3\left(y+3\right)\left(2+x\right)\left(2-x\right)\)
hoặc ghi là:
= 3(4y-3x2+12-1x2y)
cũng đúng nha