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Find the range of the function
1) Find the range of values of k for which 2x² + (k + 1) x + 18 is always positive.
13 ≤ k ≤ 11
-13 < k < 11
13 < k < -11
-13 < k < -11
1/10
Solution
Answer:
-13 < k < 11
Explanation:
Discriminant < 0 (no real solutions)
(k + 1)² – 4(2) (18) < 0
k² + 2k + 1 – 144 < 0
k² + 2k – 143 < 0
(k + 13) (k – 11) < 0
-13 < k < 11
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