Prentice Hall's Online Lesson Quiz Enter Web Code: aga–0203
A linear function written in the form y = kx , where
represents direct
variation. The slope, k, is constant. The
constant, k , is often referred to as the constant
of variation. You can write the constant of variation as a
ratio y : x .
| Ex. #1 | Determine whether y varies directly with x. If so, find the constant of variation and write the equation. | ||||||||||
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Yes, y varies directly with x. |
| Ex. #2 | Determine whether y varies directly with x. If so, find the constant of variation. |
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a. 6y = 18x |
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6y = 18x is equivalent to y = 3x, so y varies directly with x. The constant of variation is 3.
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| b. 4y – 1 = 3x | |
Since you cannot write the equation in the form of y = kx, y does not vary directly with x. |
You can use a proportion to solve some direct variation problems. If you are not asked to find the constant of variation, this is a quick method to use.
| Ex. #3 | Suppose y varies directly with x, and y = 15 when x = 27. Find y when x = 18. |
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