Solution:
( 1)x? -3x-4=0
Solution: x=4 or x=- 1.
The solution set of equation ∴ is {- 1, 4}
(2)4x+3=0
So x=-3/4.
So the set is {-3/4}
(3) Because the set consists of 1, 4,9,16,25.
So the set can be expressed as: {1, 4,9,16,25}
(4) Because the set consists of all positive odd numbers.
So the set can be expressed as: {x|x=2k- 1, k∈N+}
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