Answer:
Find the LCD of the first two, then the LCD of that and the third one.
Explanation:
You can do it by finding the LCD of two of the denominators, then the LCD of that and the third denominator.
Or, you can factor each of the denominators and find their LCM by multiplying the unique factors to their highest powers.
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Example:
1/21 + 1/35 + 1/45
The LCD of 1/21 and 1/35 is (21·35)/5 = 105. The LCD of 1/105 and 1/45 is ...
(105·45)/15 = 315
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Using factoring ...
- 21 = 3·7
- 35 = 5·7
- 45 = 3²·5
LCD = 3²·5·7 = 315