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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) b2a\frac{- b}{2a}> 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) (6a)2(1)\frac{- ( - 6a)}{2(1)}> 3 a > 1 … (3)

so, from (1), (2) and (3) a > 11/9