2a+3y−8z. x+4y+5z. 2ac+2bc. 2ab−3ac+4bc. x3+3x2+2x−8. x3−7x2+4x. 2b3+18abc−15c3. 2−x−2x2+2x3. −3b3−4c3+6abc. −x4−2x3+4x2−7x+5. 2x+x2+x3+x5. 2b3−4a2b+2ab2. 2b4−2a3b3−ab2. 4x3−3x2y−4xy2+7y3. Ejercicio 20. c. y−b. x−3y−7c. 7a+2b−2. 2a+x. 13x−15y+13z. 2a−2b+2c. 5a+b−4c. 4x−5y+2z. 3a−b. 2x+3y+z.