1. ( ax+b ) ( cx+d )=ac x 2 +( ad+bc )x+bd 2. ( x+b ) ( x+d )= x 2 +( b+d )x+bd 3. ( x+y ) 2 = x 2 +2xy+ y 2 4. ( x−y ) 2 = x 2 −2xy+ y 2 5. ( x−y ) ( x+y )= x 2 − y 2 6. ( x+y+z ) 2 = x 2 + y 2 + z 2 +2xy+2yz+2zx 7. ( x+y ) 3 = x 3 +3 x 2 y+3x y 2 + y 3 8. ( x−y ) 3 = x 3 −3 x 2 y+3x y 2 − y 3