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Beginning and Intermediate Algebra - Wallace Math Courses ...

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Example 420.<br />

ab2 3√<br />

a2 4√<br />

b<br />

Rewrite as rational exponents<br />

(ab2 ) 1<br />

3(a2b) 1<br />

4 Multiply exponents<br />

a 1<br />

3 b 2<br />

3 a 2<br />

4 b 1<br />

4 To have one radical need a common denominator, 12<br />

a 4<br />

12 b 8<br />

12 a 6<br />

12 b 3<br />

12<br />

a<br />

Write underasingle radical with common index, 12<br />

4b8a6b3 12 √<br />

12 √<br />

a 10 b 11<br />

Add exponents<br />

Our Solution<br />

To combine the radicals we need a common index (just like the common denominator).<br />

We will get a common index by multiplying each index <strong>and</strong> exponent by<br />

an integer that will allow us to build up to that desired index. This process is<br />

shown in the next example.<br />

Example 421.<br />

a2b3 4√<br />

a2 6√<br />

b<br />

a6b9a4b2 12 √<br />

12 √<br />

a 10 b 11<br />

Common index is 12.<br />

Multiply first index <strong>and</strong> exponents by 3, second by 2<br />

Add exponents<br />

Our Solution<br />

Often after combining radicals of mixed index we will need to simplify the<br />

resulting radical.<br />

Example 422.<br />

x3y4 �<br />

5<br />

x2 �<br />

3<br />

y<br />

x9y12x10y 5<br />

15 �<br />

x19y17 15 �<br />

xy x4y2 15 �<br />

Common index: 15.<br />

Multiply first index <strong>and</strong> exponents by 3, second by 5<br />

Add exponents<br />

Simplify by dividing exponents by index, remainder is left inside<br />

Our Solution<br />

Just as with reducing the index, we will rewrite coefficients as exponential expressions.<br />

This will also allow us to use exponent properties to simplify.<br />

Example 423.<br />

4x2 �<br />

3<br />

y 8xy3 4<br />

�<br />

� �<br />

3<br />

2 2 x 2 y<br />

4<br />

2 3 xy 3<br />

28x8y429x3y 9<br />

12�<br />

217x11y 13<br />

12�<br />

2y 25x11 12<br />

y<br />

�<br />

2y 32x11 12<br />

y<br />

�<br />

Rewrite 4 as2 2 <strong>and</strong> 8 as 2 3<br />

Common index: 12.<br />

Multiply first index <strong>and</strong> exponents by 4, second by 3<br />

Add exponents(even on the 2)<br />

Simplify by dividing exponents by index, remainder is left inside<br />

Simplify 2 5<br />

Our Solution<br />

315

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