x2−(a−b)x−ab. x2−(a+b)x+ab. x2+(2a+2b)x+4ab. x2−(2a−2b)x−4ab. x2+(2a−2b)x−4ab. x2−(2a+2b)x+4ab. x2+2ax−3a2. x2+ax−6a2. Exercise28. x+2. x−2. a+3. a−3. c+5. c−5. 7x+y. 7x−y. 3b+1. 3b−1. 4x2+5a. 4x2−5a. 3x+5y. a+b−c. a−b+c. a+2b−c. 5a−7b+1.