Вправи 501 - 600 » 569

Спростіть вираз: 1) (b + 7)(b – 4) + (2b – 6)(2b + 6) = b2 – 4b + 7b – 28 + (2b)2 – 62 = b2 + 3b – 28 + 4b2 – 36 = 5b2 + 3b – 64; 2) (х + 1)(х – 1) – (х + 5)(x – 5) + (х + 1)(х – 5) = х2 – 1 – (x2 – 25) + х2 – 5х + х – 5 = х2 – 1 – х2 + 25 + х2 – 5х + х – 5 = х2 – 4х + 19; 3) 81а8 – (За2 – b3)(9а4 + b6)(3а2 + b3) = 81а8 – (За2 – b3)(За2 + b3)(9а4 + b6) = 81а8 – (9а4 – b6)(9а4 + b6) = 81а8 – (81а8 – b12) = 81а8 – 81а8 + b12 = b12.