- Given function
f(x)=ln(4x2+11x+6)+sin−1(4x+3)+cos−1(310x+6)
We need the domain of this function.
For the domain, all three terms must be defined simultaneously.
- Condition from the logarithm
For ln(4x2+11x+6) to be defined,
4x2+11x+6>0
Factorize:
4x2+11x+6=(4x+3)(x+2)
So we need
(4x+3)(x+2)>0
Critical points are x=−2 and x=−43.
Thus,
x∈(−∞,−2)∪(−43,∞)
- Condition from sin−1(4x+3)
For sin−1(4x+3) to be defined,
−1≤4x+3≤1
Subtract 3:
−4≤4x≤−2
Divide by 4:
−1≤x≤−21
- Condition from cos−1(310x+6)
For cos−1(y) to be defined,
−1≤y≤1
So,
−1≤310x+6≤1
Multiply by 3:
−3≤10x+6≤3
Subtract 6:
−9≤10x≤−3
Divide by 10:
−109≤x≤−103
- Intersect all conditions
We need
x∈[−1,−21]∩[−109,−103]∩[(−∞,−2)∪(−43,∞)]
First intersect the inverse trigonometric conditions:
[−1,−21]∩[−109,−103]=[−109,−21]
Now intersect with the logarithm condition:
[−109,−21]∩[(−∞,−2)∪(−43,∞)]
Since [−109,−21] does not meet (−∞,−2), only the second part matters:
[−109,−21]∩(−43,∞)=(−43,−21]
So the domain is
(α,β]=(−43,−21]
Hence,
α=−43,β=−21
- Compute 36∣α+β∣
α+β=−43−21=−43−42=−45
Therefore,
∣α+β∣=45
So,
36∣α+β∣=36⋅45=9⋅5=45
- Option check
The value is
45
So the correct option is C.