А)(х-2)²-4=х²-4х+4-4=х²-4х
б)(b+7)²-100c²=b²+14b+49-100c²=14b³+49-100c²
в)121-(b+7)²=121-b²+14b+49=170-14b³
г)a⁴-(7b-a²)²=a⁴-49b²-14ba²+a⁴=a⁸-49b²-14ba²
д)(4х-9)²-(2х+19)²=16х²-72х-4х²+76х+361=12х²-4х+361
е)(a+b+c)²-(a-b-c)²=a²+b²+2abc+c²-a²+b²+2abc-c²=b⁴+4abc