If 10 4 + 15 4 = 6, then the value of 27 cosec6 + 8 6 16 8 is
- 25
- 35
- 15
- 34
Answer
(1) 25
Solution
Let 2 = t, so 2 = 1 - t:
10t2 + 15(1 - t)2 = 6
⇒ 25t2 - 30t + 9 = 0
⇒ (5t - 3)2 = 0 ⇒ t = 35
∴ 2 = 35, 2 = 25
cosec6 = ( 53 )3 = 12527, 6 = ( 52 )3 = 1258, 8 = ( 52 )4 = 62516
Required value = 27 12527 + 8 125816 62516
= 250625 = 25
Answer: (1)