已知2已知2
已知2∫(1~2) (kx + 1) dx= kx²/2 + x |(1~2)= (2k + 2) - (k/2 + 1)= 3k/2 + 12 ≤ ∫(1~2) (kx + 1) dx ≤ 42 ≤ 3k/2 + 1 ≤ 42/3 ≤ k ≤ 2