Question:

If $\log _{e}\left(x^{2}-16\right) \leq \log _{e}(4 x-11)$, then

Updated On: Apr 26, 2024
  • $4
  • $x\, 4$
  • $-1 \le x\le5$
  • $x\, 5$
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The Correct Option is A

Solution and Explanation

Given, $\log _{e}\left(x^{2}-16\right) \leq \log _{e}(4 x-11)$ if and only if $x^{2}-16 \leq 4 x-11$ $\Rightarrow x^{2}- 4 x-5 \leq 0$ $x^{2}-5 x+x-5 \leq 0$ $\Rightarrow x(x-5)+1(x-5) \leq 0$ $(x-5)(x+1) \leq 0$ Sign scheme of $x^{2}-4 x-5 \leq 0$
$-1 \leq x \leq 5$
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Concepts Used:

Exponential and Logarithmic Functions

Logarithmic Functions:

The inverses of exponential functions are the logarithmic functions. The exponential function is y = ax and its inverse is x = ay. The logarithmic function y = logax is derived as the equivalent to the exponential equation x = ay. y = logax only under the following conditions: x = ay, (where, a > 0, and a≠1). In totality, it is called the logarithmic function with base a.

The domain of a logarithmic function is real numbers greater than 0, and the range is real numbers. The graph of y = logax is symmetrical to the graph of y = ax w.r.t. the line y = x. This relationship is true for any of the exponential functions and their inverse.

Exponential Functions:

Exponential functions have the formation as:

f(x)=bx

where,

b = the base

x = the exponent (or power)