Part (a)
Answer: ad = bc
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Explanation:
In the equation a/b = c/d, we have b and d in the denominator.
If we multiply both sides by bd, then the denominators will cancel. The expression bd is the same as bd/1.
As a similar example, consider the equation
a/b = 12
if we multiply both sides by b, then we clear out the denominator to end up with a = 12b
As another example, let's consider
a/b = c
Multiplying both sides by b leads to
a = bc
The same idea applies with the denominator d as well.
When going from a/b = c/d to ad = bc, your textbook may refer to this process as "cross multiplication".
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Part (b)
Answer: bd is the product of the denominators
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Explanation:
Often in math, writing two variables next to each other represents multiplication.
bd is the same as b*d which means "b times d". The term "product" is the result of multiplying two or more values.
b and d are both in the denominator of each fraction, so bd represents the product of the denominators.
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