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Given two fractions, you find the Least Common Denominator by finding the Least Common Multiple of the two Denominators. Then for each fraction, the new numerator the product of the is old numerator, and whatever multiplier you use to get the new denominator.
Example: 1/14 - 1/21: The LCM of 14 & 21 is 42, so for the first fraction: 3 x 14 = 42, so the new numerator is 3 x 1 = 3.
For the 2nd fraction: 2 x 21 = 42, so the new numerator is 2 x 1 = 2. The new subtraction problem is: 3/42 - 2/42 = 1/42
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How do you add similar rational algebraic expressions?
Lcd/lcm
If you are adding or subtracting rational expressions with different polynomial expressions in the denominator explain how you would find the LCD.?
One way is to simply multiply the denominators together. That won't give you the LEAST common denominator, but it will give you A common denominator.You can also use one of the several methods explained in the Wikipedia article on "Least common multiple". For example, you can split each number up into prime factors, and multiply all the unique prime factors together. If a prime factor appears more than once in some of the numbers, use the highest power.
What is the importance of reducing fractions to lowest term?
In order to find the LCD when adding or subtracting fractions
When do you use LCD in math?
When adding or subtracting fractions with different denominators then their LCD must be found in order to carry out the calculations.
Can you always cross multiply rational expressions?
If you need to simplify a rational expression with two or more terms, you need to find the LCD in order to write the expression as a single fraction. If the denominators have not common factors, then the only way is to multiply each numerator with the all denominators of the other terms. If you have an equation in the proportion form, then cross multiply. If both sides of the equation have more than two rational terms, then work at both sides until you have a proportion, then cross multiply. But I would prefer to multiply each term at both sides by the LCD in order to eliminate the denominators.
