Question
Question: If x<sup>2</sup> + 2ax + 10 – 3a \> 0 for all x Ī R, then –...
If x2 + 2ax + 10 – 3a > 0 for all x Ī R, then –
A
– 5 < a < 2
B
a < – 5
C
a > 5
D
2 < a < 5
Answer
– 5 < a < 2
Explanation
Solution
x2 + 2ax + 10 – 3a > 0
Ž D < 0 Ž 4a2 – 4(10–3a)<0 Ž a2 – 10 + 3a < 0
a + 3a – 10 < 0 Ž (a + 5) (a–2) < 0 Ž a Ī (–5, 2)