Question
Question: If both roots of the equation x<sup>2</sup> – 6ax + 2 –2a + 9a<sup>2</sup> = 0, exceed 3, then a is-...
If both roots of the equation x2 – 6ax + 2 –2a + 9a2 = 0, exceed 3, then a is-
A
Less than 11/9
B
Greater than 7/9
C
Greater than 5/9
D
Greater than 11/9
Answer
Greater than 11/9
Explanation
Solution
(i) D ³ 0 (ii) (1) f(3) > 0 (iii) 2a−b> 3
(i) 36a2 – 4(2 –2a + 9a2) ³ 0
a ³ 1 …(1)
(ii) (1) (9 – 18a + 2 – 2a + 9a2) > 0 (9a – 11) (a –1) > 0
a Ī (– , 1) Č (11/9, ) … (2)
(iii) 2(1)−(−6a)> 3 a > 1 … (3)
so, from (1), (2) and (3) a > 11/9