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Ответ:

3.

1) = 16a⁴+20a⁴y

2) = 2x³c³-20c²-14c³+4c⁶

3) = 2y⁴a-2y⁴-3y³b

4.

12c(3c+4)-(24c²-14c)-62c=0

36c²+48-24c²+14c-62c=0

12c²-48c+48=0. |:12

c²-4c+4=0

По т.Виета:

x1 = 2

х2 = 2