求题目解!快

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求题目解!快
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求题目解!快
求题目解!快

 

求题目解!快
f'(x) = [ 8x(2-x) - (4x²-7)*(-1) ] / (2-x)²
= (-4x² +16x - 7 ) / (2-x)²
令f'(x) = 0得 x = 1/2,7/2
x 0 (0,1/2) 1/2 (1/2,1) 1
f'(x) 0
f(x) - 7/2 递减 - 4 递增 - 3
减区间(0,1/2) 增区间 (1/2,1)
值域 [-4,-3]
f(x) ≤ m² - 2m - 7 有解
只需 m² - 2m - 7 ≥ f(x)的最小值 = - 4
m² - 2m - 3 ≥ 0
(m+1)(m-3) ≥ 0
m ≤ - 1 或 m ≥ 3