NIMCET 2019 — Mathematics PYQ
NIMCET | Mathematics | 2019Solution set of inequality \log_{3}(x+2)(x+4)+\log_{\frac{1}{3}}(x+2)<\frac{1}{2}\log_{\sqrt{3}}7 is
Choose the correct answer:
- A.
(-2, -1)
- B.
(-2, 3)
(Correct Answer) - C.
(-1, 3)
- D.
(3, ∞)
(-2, 3)
Explanation
Concept:
- logαβm=β1logαm
- logαnm=logαm−logαn
- If logαm=logαn then m=n
Calculation:
\log_{3}(x+2)(x+4)+\log_{\frac{1}{3}}(x+2)<\frac{1}{2}\log_{\sqrt{3}}7
As we know that, logαm=β1logαm
\log_{3} (x + 2) (x + 4) - \log_{3} (x + 2) < \log_{3} 7
As we know that, logαnm=logαm−logαn
\log_{3} (x + 4) < \log_{3} 7
As we know that, if logαm=logαn then m=n
\Rightarrow x + 4 < 7
\Rightarrow x < 3 ------------(1)
For log3(x+2)(x+4) to exist x∈(−2,∞)-------------(2)
For log3(x+2)⇒x∈(−2,∞)-------------(3)
By combining equation 1, 2, 3 we get x∈(−2,3)
Explanation
Concept:
- logαβm=β1logαm
- logαnm=logαm−logαn
- If logαm=logαn then m=n
Calculation:
\log_{3}(x+2)(x+4)+\log_{\frac{1}{3}}(x+2)<\frac{1}{2}\log_{\sqrt{3}}7
As we know that, logαm=β1logαm
\log_{3} (x + 2) (x + 4) - \log_{3} (x + 2) < \log_{3} 7
As we know that, logαnm=logαm−logαn
\log_{3} (x + 4) < \log_{3} 7
As we know that, if logαm=logαn then m=n
\Rightarrow x + 4 < 7
\Rightarrow x < 3 ------------(1)
For log3(x+2)(x+4) to exist x∈(−2,∞)-------------(2)
For log3(x+2)⇒x∈(−2,∞)-------------(3)
By combining equation 1, 2, 3 we get x∈(−2,3)

