Calculate the Result of the Fractions and Powers: 1/(-3)·3^(-4)·5^3

Question

133453=? \frac{1}{-3}\cdot3^{-4}\cdot5^3=\text{?}

Video Solution

Solution Steps

00:00 Solve the following problem
00:02 According to the laws of exponents, a number (A) raised to the power of (-N)
00:05 equals 1 divided by the number (A) raised to the power of (N)
00:08 Let's apply this to (3) raised to the power of (-4)
00:11 We obtain 1 divided by (3) raised to the power of (4)
00:21 According to the laws of exponents, a number (A) raised to the power of (M)
00:24 multiplied by the same number (A) raised to the power of (N)
00:27 equals the number (A) raised to the power of (M+N)
00:30 Let's apply this to the question and combine the exponents of the denominators
00:35 Let's calculate the power
00:46 This is the solution

Step-by-Step Solution

First we'll use the laws of exponents for negative exponents, but in the opposite direction:

1an=an \frac{1}{a^n} = a^{-n} and we'll handle the leftmost term in the multiplication:

133453=133453=313453 \frac{1}{-3}\cdot3^{-4}\cdot5^3=-\frac{1}{3}\cdot3^{-4}\cdot5^3=-3^{-1}\cdot3^{-4}\cdot5^3 where in the first step we simplified the first fraction while remembering that dividing a positive number by a negative number gives a negative result, and in the second step we applied the aforementioned law of exponents,

Before we continue, let's note and emphasize that the minus sign is not under the exponent in the first term of the multiplication, meaning - the exponent doesn't apply to it but only to the number 3.

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 we got:

313453=31+(4)53=31453=3553 -3^{-1}\cdot3^{-4}\cdot5^3=-3^{-1+(-4)}\cdot5^3=-3^{-1-4}\cdot5^3=-3^{-5}\cdot5^3 when we applied the aforementioned law of exponents only to the terms with identical bases and carried the minus sign throughout the calculation for the reason we mentioned earlier,

Let's summarize the steps so far, we got:

133453=313453=31453=3553 \frac{1}{-3}\cdot3^{-4}\cdot5^3=-3^{-1}\cdot3^{-4}\cdot5^3 =-3^{-1-4}\cdot5^3=-3^{-5}\cdot5^3

Note that this answer isn't among the answer choices, however, we can now apply again the negative exponent law:

an=1an a^{-n}=\frac{1}{a^n} and we'll apply it to the first term in the multiplication of terms we got in the last step:

3553=13553=5335 -3^{-5}\cdot5^3=-\frac{1}{3^5}\cdot5^3=-\frac{5^3}{3^5} where in the first step we applied the aforementioned law to the first term in the multiplication, and in the next step we performed the fraction multiplication while remembering that multiplying by a fraction is essentially multiplying by the numerator,

Let's summarize the solution steps again:
133453=313453=3553=5335 \frac{1}{-3}\cdot3^{-4}\cdot5^3=-3^{-1}\cdot3^{-4}\cdot5^3 =-3^{-5}\cdot5^3 =-\frac{5^3}{3^5}

Therefore, the correct answer is answer B.

Answer

5335 -\frac{5^3}{3^5}