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Direct Variations. Vocabulary. Direct Variation When two variables form a constant ratio Equation: y = kx (where k is the constant ratio) Constant of variation The ratio k = y / x (note similarity to slope ratio). Direct Variation Identification. From a graph
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Vocabulary • Direct Variation • When two variables form a constant ratio • Equation: y = kx (where k is the constant ratio) • Constant of variation • The ratio k = y/x (note similarity to slope ratio)
Direct Variation Identification • From a graph • If the graph crosses the y-axis at (0,0), then the relationship is a direct variation • If the graph crosses the y-axis at any other point, then the relationship is NOT a direct variation
Direct Variation Graphs y = 3x – 1 y = 3x
Direct Variation Identification • From a table • If the ratios, y/x, in the table are proportional, then the relationship is a direct variation • If even one of the ratios, y/x, in the table is NOT proportional, then the relationship is NOT a direct variation
Direct Variation Tables Determine whether each linear function is a direct variation. If so, state the constant of variation.
Direct Variation Tables Determine whether each linear function is a direct variation. If so, state the constant of variation.