Divide Monomials

You have now been introduced to all the properties of exponents and used them to simplify expressions. Next, you'll see how to use these properties to divide monomials. Later, you'll use them to divide polynomials.

Example 6.72

Find the quotient: \(56 x^{7} \div 8 x^{3}\).

Solution
  \(56 x^{7} \div 8 x^{3}\)
Rewrite as a fraction. \(\dfrac{56 x^{7}}{8 x^{3}}\)
Use fraction multiplication. \(\dfrac{56}{8} \cdot \dfrac{x^{7}}{x^{3}}\)
Simplify and use the Quotient Property. \(7 x^{4}\)
Try It 6.143

Find the quotient: \(42 y^{9} \div 6 y^{3}\).

Try It 6.144

Find the quotient: \(48 z^{8} \div 8 z^{2}\).

Example 6.73

Find the quotient: \(\dfrac{45 a^{2} b^{3}}{-5 a b^{5}}\).

Solution
  \(\dfrac{45 a^{2} b^{3}}{-5 a b^{5}}\)
Use fraction multiplication. \(\dfrac{45}{-5} \cdot \dfrac{a^{2}}{a} \cdot \dfrac{b^{3}}{b^{5}}\)
Simplify and use the Quotient Property. \(-9 \cdot a \cdot \dfrac{1}{b^{2}}\)
Multiply. \(-\dfrac{9 a}{b^{2}}\)
Try It 6.145

Find the quotient: \(\dfrac{-72 a^{7} b^{3}}{8 a^{12} b^{4}}\).

Try It 6.146

Find the quotient: \(\dfrac{-63 c^{8} d^{3}}{7 c^{12} d^{2}}\).

Example 6.74

Find the quotient: \(\dfrac{24 a^{5} b^{3}}{48 a b^{4}}\).

Solution
  \(\dfrac{24 a^{5} b^{3}}{48 a b^{4}}\)
Use fraction multiplication. \(\dfrac{24}{48} \cdot \dfrac{a^{5}}{a} \cdot \dfrac{b^{3}}{b^{4}}\)
Simplify and use the Quotient Property. \( \dfrac{1}{2} \cdot a^{4} \cdot \dfrac{1}{b} \)
Multiply. \(\dfrac{a^{4}}{2 b}\)
Try It 6.147

Find the quotient: \(\dfrac{16 a^{7} b^{6}}{24 a b^{8}}\).

Try It 6.148

Find the quotient: \(\dfrac{27 p^{4} q^{7}}{-45 p^{12} q}\).

Once you become familiar with the process and have practiced it step by step several times, you may be able to simplify a fraction in one step.

Example 6.75

Find the quotient: \(\dfrac{14 x^{7} y^{12}}{21 x^{11} y^{6}}\).

Solution

Be very careful to simplify 1421 by dividing out a common factor, and to simplify the variables by subtracting their exponents.

  \(\dfrac{14 x^{7} y^{12}}{21 x^{11} y^{6}}\)
Simplify and use the Quotient Property. \(\dfrac{2 y^{6}}{3 x^{4}}\)
Try It 6.149

Find the quotient: \(\dfrac{28 x^{5} y^{14}}{49 x^{9} y^{12}}\).

Try It 6.150

Find the quotient: \(\dfrac{30 m^{5} n^{11}}{48 m^{10} n^{14}}\).

In all Examples so far, there was no work to do in the numerator or denominator before simplifying the fraction. In the next Example, we'll first find the product of two monomials in the numerator before we simplify the fraction. This follows the order of operations. Remember, a fraction bar is a grouping symbol.

Example 6.76

Find the quotient: \(\dfrac{\left(6 x^{2} y^{3}\right)\left(5 x^{3} y^{2}\right)}{\left(3 x^{4} y^{5}\right)}\).

Solution
  \(\dfrac{\left(6 x^{2} y^{3}\right)\left(5 x^{3} y^{2}\right)}{\left(3 x^{4} y^{5}\right)}\)
Simplify the numerator. \(\dfrac{30 x^{5} y^{5}}{3 x^{4} y^{5}}\)
Simplify. \(10x\)
Try It 6.151

Find the quotient: \(\dfrac{\left(6 a^{4} b^{5}\right)\left(4 a^{2} b^{5}\right)}{12 a^{5} b^{8}}\).

Try It 6.152

Find the quotient: \(\dfrac{\left(-12 x^{6} y^{9}\right)\left(-4 x^{5} y^{8}\right)}{-12 x^{10} y^{12}}\).