Solve the Exponential Expression: 4^(2x) × (1/4) × 4^(-2)

Exponential Laws with Negative Exponents

Solve the following problem:

42x1442=? 4^{2x}\cdot\frac{1}{4}\cdot4^{-2}=\text{?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:10 Let's solve this problem.
00:13 Remember, a number A raised to the power of negative N,
00:18 means 1 divided by A to the power of positive N.
00:22 For example, 1 over 4 is the same as 4 to the power of negative 1.
00:29 Now, let's use this in our question.
00:37 When we multiply A to the M by A to the N,
00:42 we get A to the power of M plus N.
00:46 Let's apply and combine the exponents.
00:49 Use the formula to convert it to a fraction.
00:57 We get 1 divided by 4 to the power of negative 2X minus 3.
01:03 Continue to simplify the expression further.
01:10 And that's how we find the solution!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following problem:

42x1442=? 4^{2x}\cdot\frac{1}{4}\cdot4^{-2}=\text{?}

2

Step-by-step solution

Apply the laws of exponents for negative exponents, in the opposite direction:

1an=an \frac{1}{a^n} = a^{-n}

to the middle term in the multiplication in the problem:

42x1442=42x4142 4^{2x}\cdot\frac{1}{4}\cdot4^{-2}=4^{2x}\cdot4^{-1}\cdot4^{-2}

Next, we'll recall the law of exponents for multiplication of terms with identical bases:

aman=am+n a^m\cdot a^n=a^{m+n}

and we'll apply this law to the last expression that we obtained :

42x4142=42x+(1)+(2)=42x12=42x3 4^{2x}\cdot4^{-1}\cdot4^{-2}=4^{2x+(-1)+(-2)}=4^{2x-1-2}=4^{2x-3}

We obtained the most simplified expression,

Let's summarize the steps so far, as follows:

42x1442=42x4142=42x3 4^{2x}\cdot\frac{1}{4}\cdot4^{-2}=4^{2x}\cdot4^{-1}\cdot4^{-2} =4^{2x-3}

A quick look at the options will reveal that there isn't such an answer among the options and another check of what we've done so far will show that there are no calculation errors,

This means that another mathematical manipulation is needed on the expression we got, a hint for the required manipulation could be the fact that answer D is similar to our expression but the exponent has a minus sign compared to the exponent we got in the final expression and the expression itself is in a fraction where the numerator is 1, which reminds us of the negative exponent law, let's check this suspicion and handle the expression we got in the following way:

42x3=4(2x+3)=4(3+(2x))=4(32x) 4^{2x-3}=4^{-(-2x+3)}=4^{-(3+(-2x))}=4^{-(3-2x)}

The goal is to present the expression that we obtained in the form of a term with a negative exponent. We did this by taking the minus sign outside the parentheses in the exponent and rearranging the expression inside the parentheses using the commutative law of addition and then simplified the expression in parentheses,

Now let's use the negative exponent law again:

an=1an a^{-n} =\frac{1}{a^n}

And apply it to the expression that we obtained:

4(32x)=1432x 4^{-(3-2x)}=\frac{1}{4^{3-2x}}

Therefore the expression that we obtained earlier can be written as:

42x1442=42x3=4(32x)=1432x 4^{2x}\cdot\frac{1}{4}\cdot4^{-2} =4^{2x-3} = 4^{-(3-2x)}=\frac{1}{4^{3-2x}}

The correct answer is indeed answer D.

3

Final Answer

1432x \frac{1}{4^{3-2x}}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Convert fractions to negative exponents: 1an=an \frac{1}{a^n} = a^{-n}
  • Technique: Combine same bases by adding exponents: 42x4142=42x3 4^{2x} \cdot 4^{-1} \cdot 4^{-2} = 4^{2x-3}
  • Check: Transform negative exponent back to fraction form: 4(32x)=1432x 4^{-(3-2x)} = \frac{1}{4^{3-2x}}

Common Mistakes

Avoid these frequent errors
  • Forgetting to convert 1/4 to negative exponent form
    Don't leave 1/4 as a fraction while combining = mixed notation confusion! This prevents you from using exponent laws properly and leads to incomplete solutions. Always convert all terms to exponential form first: 14=41 \frac{1}{4} = 4^{-1} .

Practice Quiz

Test your knowledge with interactive questions

\( 112^0=\text{?} \)

FAQ

Everything you need to know about this question

Why do I need to convert 1/4 to 4^(-1)?

+

Converting 14 \frac{1}{4} to 41 4^{-1} lets you use the same base rule for multiplication! When all terms have base 4, you can add the exponents directly.

How do I add negative exponents?

+

Treat negative exponents like regular numbers when adding: 2x+(1)+(2)=2x12=2x3 2x + (-1) + (-2) = 2x - 1 - 2 = 2x - 3 . The negative signs stay with their numbers!

Why does my answer look different from the choices?

+

Sometimes you need to transform your answer using exponent laws! If you got 42x3 4^{2x-3} , rewrite it as 4(32x) 4^{-(3-2x)} , then convert to 1432x \frac{1}{4^{3-2x}} .

When should I use the negative exponent law?

+

Use an=1an a^{-n} = \frac{1}{a^n} when you need to match answer formats. If choices show fractions, convert your exponential form to fraction form!

How do I check if 4^(2x-3) equals 1/4^(3-2x)?

+

Rewrite 42x3 4^{2x-3} as 4(32x) 4^{-(3-2x)} by factoring out the negative. Then apply an=1an a^{-n} = \frac{1}{a^n} to get 1432x \frac{1}{4^{3-2x}} !

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