Question

How do you solve \[{25^{2x + 3}} = {125^{x - 4}}\] ?

Answer 1

Hint: Here in this question, we have to solve this question. The given question is in the form of an exponential number. It is defined as the number of times the number is multiplied by itself. By using the definition of exponential number and the law of indices we are solving the given question.

Complete step-by-step answer:
The exponential number is defined as the number of times the number is multiplied by itself. Here we have to find the value of x. Consider the given equation
 \[{25^{2x + 3}} = {125^{x - 4}}\] ------- (1)
Here in the above equation the two terms present in LHS and RHS of the equation are the multiples of 5.
The exponential form of 25 is written as \[{5^2}\] ---- (2)
And the exponential form of 125 is written as \[{5^3}\] ------ (3)
Substitute the equation (2) and the equation (3) in the equation (1). So the given equation is rewritten as
 \[ \Rightarrow {5^{2(2x + 3)}} = {5^{3(x - 4)}}\]
Hence by simplifying the exponents of the above equation.
 \[ \Rightarrow {5^{4x + 6}} = {5^{3x - 12}}\]
According to the properties of exponential numbers, if the value of the base is the same then we can equate the exponents. So we can write the above equation as
 \[ \Rightarrow 4x + 6 = 3x - 12\]
Take 3x to the LHS and take 6 to RHS, the equation can be written as
 \[ \Rightarrow 4x - 3x = - 12 - 6\]
On simplification we have
 \[ \Rightarrow x = - 18\]
Therefore, we have solved the given question and obtained the value of x
Therefore \[x = 18 \]
So, the correct answer is “ \[x = 18\] ”.

Note: The exponential number is an inverse of the logarithmic function. To solve we can apply the log on both sides but here we have used the definition of the exponential number we convert the number to the exponential number. The law of indices is used to solve these kinds of problems.