Q.

Let the domain of the function f(x)=log3log5 (7-log2(x2-10x+85))+sin-1 (|3x-717-x|)  be (α,β]. Then α+β is equal to:     [2026]

1 8  
2 10  
3 9  
4 12  

Ans.

(3)

Let x2-10x+85=λ

∴ Domain for first term

λ>0    ...(1)

&  7-log2λ>0⇒λ<27    ...(2)

&  log5(7-log2λ)>0⇒λ<26    ...(3)

∴ from (1), (2) & (3)

0<λ<26

0<x2-10x+85<64

⇒x∈(3,7)    ...(A)

& domain for second term -1≤3x-7x-17≤1

⇒x∈[-5,6]    ...(B)

From (A) & (B), domain of function will be (3,6]

⇒α=3, β=6

⇒α+β=9