12) 8npq+7 -7-8npq

12) a = 8npq + 7, b = -7 - 8npq

a + b = (8npq + 7) + (-7 - 8npq) = 8npq + 7 - 7 - 8npq = 0

a - b = (8npq + 7) - (-7 - 8npq) = 8npq + 7 + 7 + 8npq = 16npq + 14

Ответ: a + b = 0, a - b = 16npq + 14