1)
ab+ac= a ( b + c )
2)
ab - ac + ad= a ( b - a + d )
3)
ax - bx - cx + dx= x ( a - b - c + d )
4)
a(b + c) - d(b + c)= ( a - d ) . (b + c )
5)
ac - ad + bc - bd= a ( c - d ) + b ( c - d )
= ( a + b ) . ( c - d )
6)
ax + by + bx + ay= x . ( a + b ) + y . ( a + b )
= ( x + y ) . ( a + b )
~Học tốt~