Examples with solutions for Applying Combined Exponents Rules: Presenting powers with negative exponents as fractions

Exercise #1

192=? 19^{-2}=\text{?}

Video Solution

Step-by-Step Solution

In order to solve the exercise, we use the negative exponent rule.

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

We apply the rule to the given exercise:

192=1192 19^{-2}=\frac{1}{19^2}

We can then continue and calculate the exponent.

1192=1361 \frac{1}{19^2}=\frac{1}{361}

Answer

1361 \frac{1}{361}

Exercise #2

25=? 2^{-5}=\text{?}

Video Solution

Step-by-Step Solution

We begin by using the power rule of negative exponents.

an=1an a^{-n}=\frac{1}{a^n} We then apply it to the problem:

25=125=132 2^{-5}=\frac{1}{2^5}=\frac{1}{32} We can therefore deduce that the correct answer is option A.

Answer

132 \frac{1}{32}

Exercise #3

41=? 4^{-1}=\text{?}

Video Solution

Step-by-Step Solution

We begin by using the power rule of negative exponents.

an=1an a^{-n}=\frac{1}{a^n} We then apply it to the problem:

41=141=14 4^{-1}=\frac{1}{4^1}=\frac{1}{4} We can therefore deduce that the correct answer is option B.

Answer

14 \frac{1}{4}

Exercise #4

724=? 7^{-24}=\text{?}

Video Solution

Step-by-Step Solution

Using the rules of negative exponents: how to raise a number to a negative exponent:

an=1an a^{-n}=\frac{1}{a^n} We apply it to the problem:

724=1724 7^{-24}=\frac{1}{7^{24}} Therefore, the correct answer is option D.

Answer

1724 \frac{1}{7^{24}}

Exercise #5

(7)3=? (-7)^{-3}=\text{?}

Video Solution

Step-by-Step Solution

We begin by using the power property for a negative exponent:

bn=1bn b^{-n}=\frac{1}{b^n} We apply it to the problem:

(7)3=1(7)3 (-7)^{-3}=\frac{1}{(-7)^3} We then subsequently notice that each whole number inside the parentheses is raised to a negative power (that is, the number and its negative coefficient together) When using the previously mentioned power property: We are careful to take this into account,

We then continue by simplifying the expression in the denominator of the fraction, remembering the exponentiation property for the power of terms in multiplication:

(am)n=amn (a^m)^n=a^{m\cdot n} We apply the resulting expression

1(7)3=1(17)3=1(1)373=1173=173=173 \frac{1}{(-7)^3}=\frac{1}{(-1\cdot7)^3}=\frac{1}{(-1)^3\cdot7^3}=\frac{1}{-1\cdot7^3}=\frac{1}{-7^3}=-\frac{1}{7^3}

In summary we are able to deduce that the solution to the problem is as follows:

(7)3=1(7)3=173=173 (-7)^{-3}=\frac{1}{(-7)^3}=\frac{1}{-7^3}=-\frac{1}{7^3}

Therefore, the correct answer is option B.

Answer

173 -\frac{1}{7^{3}}

Exercise #6

82x=? 8^{-2x}=\text{?}

Video Solution

Step-by-Step Solution

Let's use the law of exponents for negative exponents:

an=1an a^{-n}=\frac{1}{a^n} and apply it to our problem:

82x=182x 8^{-2x}=\frac{1}{8^{2x}} Next, we'll use the law of exponents for power of a power:

(am)n=amn (a^m)^n=a^{m\cdot n} and apply this law to the denominator in the expression we got:

182x=1(82)x=164x \frac{1}{8^{2x}}=\frac{1}{(8^2)^x}=\frac{1}{64^x} where we actually used the above law in the opposite direction, meaning instead of expanding the parentheses and multiplying by the power exponent, we interpreted the multiplication by the power exponent as a power of a power, and in the final stage we calculated the power inside the parentheses in the denominator.

Let's summarize the solution steps, we got that:

82x=182x=164x 8^{-2x}= \frac{1}{8^{2x}}=\frac{1}{64^x}

Therefore, the correct answer is answer D.

Answer

164x \frac{1}{64^x}

Exercise #7

a4=? a^{-4}=\text{?}

(a0) (a\ne0)

Video Solution

Step-by-Step Solution

We begin by using the negative exponent rule.

bn=1bn b^{-n}=\frac{1}{b^n} We apply it to the problem:

a4=1a4 a^{-4}=\frac{1}{a^4} Therefore, the correct answer is option B.

Answer

1a4 \frac{1}{a^4}

Exercise #8

xa=? x^{-a}=\text{?}

Video Solution

Step-by-Step Solution

We use the exponential property of a negative exponent:

bn=1bn b^{-n}=\frac{1}{b^n} We apply it to the problem:

xa=1xa x^{-a}=\frac{1}{x^a} Therefore, the correct answer is option C.

Answer

1xa \frac{1}{x^a}