1-1) -4 ≤ f'(x) < 0
1-2) 증명
1-3) 3/루트 어쩌구

2-1)2C
2-2)0 < k  ≤ 루트2
2-3) x^3+4/1x+4/1

3-1) C
3-2) 1/루트2ec
3-3) 못품

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