=[x2-6xy+(3y)2-49]
=[(x-3y)2-72]
=(x-3y-7)*(x+3y+7)
= x^2 - 6xy + 9y^2 - 49
= x^2 - 6xy + ( 3y )^2 - 49
= (x - 3y)^2 - 7^2
= (x - 3y -7)( x-3y +7) tk cho mk nha
\(x^2-49-6xy+9y^2\)
\(=\left(x^2-6xy+9y^2\right)-7^2\)
\(=\left(x-3y\right)^2-7^2\)
\(=\left(x-3y-7\right)\left(x-3y+7\right)\)
k mk nha ^_^