<h2>
Answer: </h2>
Third choice, option C
x = 5/2
To solve for the value of x<em> </em>if <em>9^(x-1) - 2 = 25</em>, we can substitute each of the options into a simplified equation.
<h2>Simplify the equation</h2>
We <em>could </em>substitute each option into the given equation, but then we would have to simplify it four more times. It's easier to simplify once first.
Start with the given equation
Add 2 to both sides
–2 + 2 on the left side cancels out
Add on the right side
We found a simplified equation.
<h2>Substitute</h2>
Now, let's substitute each option choice for 'x' in the simplified equation. We only have to substitute choices until we find the choice that makes the left and right sides of the equation equal, but let's try all of the choices today.
<h3>Option A: x = 1/2</h3>
Start with the simplified equation
Substitute x = 1/2
Find a common denominator within the exponent
Combine numerators and subtract
Convert 9 into a base and exponent
Multiply exponents
Combine into numerator
Simplify the fraction
Use negative exponent rule to simplify
Simplify the denominator
Left and right sides are <u>not equal</u>
So, <em>x</em> is not equal to 1/2.
<h3>Option B: x = 2</h3>
Start with the simplified equation
Substitute x = 2
Subtract within the exponent
Left and right sides are <u>not equal</u>
So, <em>x</em> is not equal to 2.
<h3>Option C: x = 5/2</h3>
Start with the simplified equation
Substitute x = 5/2
Find a common denominator within the exponent
Combine numerators and subtract
Use fractional exponent rule to simplify
Solve the exponent by multiplying bases
Solve the root
Left and right sides are <u>equal</u>
So, <em>x</em> is equal to 5/2.
<h3>Option D: x = 4</h3>
Start with the simplified equation
Substitute x = 4
Subtract within the exponent
Solve the exponent by multiplying bases
Left and right sides are <u>not equal</u>
So, <em>x</em> is not equal to 4.
∴ in
, <em>x</em> is equal to
, making option C correct.
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