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Learn how to identify direct variation equations and determine the constant of variation. Practice exercises provided.
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a. 2x – 3y = 0 b. –x + y = 4 EXAMPLE 1 Identify direct variation equations Tell whether the equation represents direct variation. If so, identify the constant of variation.
2 2 x y = 3 3 2x – 3y = 0 ANSWER Because the equation 2x – 3y = 0 can be rewritten in the form y = ax, it represents direct variation. The constant of variation is . EXAMPLE 1 Identify direct variation equations SOLUTION To tell whether an equation represents direct variation, try to rewrite the equation in the form y = ax. Write original equation. –3y = –2x Subtract 2x from each side. Simplify.
ANSWER Because the equation –x + y = 4 cannot be rewritten in the form y = ax, it does not represent direct variation. EXAMPLE 1 Identify direct variation equations b. Write original equation. –x + y = 4 y = x + 4 Add xto each side.
ANSWER not direct variation for Example 1 GUIDED PRACTICE Tell whether the equation represents direct variation. If so, identify the constant of variation. 1. –x + y = 1
ANSWER direct variation; –2 for Example 1 GUIDED PRACTICE Tell whether the equation represents direct variation. If so, identify the constant of variation. 2. 2x +y = 0
ANSWER 4 direct variation; 5 for Example 1 GUIDED PRACTICE Tell whether the equation represents direct variation. If so, identify the constant of variation. 3. 4x – 5y = 0