2. Direct Variation y = mx (no b) Lines that go through the origin Y intercept of zero Slope also called constant of variation (variation constant)

3. Examples of Direct Variation y = -2xy = 2x

4. Checking for Direct Variation Graph --> is it a straight line through the origin? Equation --> does it fit y = mx? (may need to solve for y)

5. Do these lines illustrate direct variation? y = - 1 / 2 xx = -3

6. What is the variation constant? y = - 1 / 2 xx = -3

7. Are these equations direct variation? y = 5x y = - 3 / 4 x y = -2x - 7

8. Are these equations direct variation? y = 5x--> Yes! y = - 3 / 4 x--> Yes! y = -2x - 7--> No (y-int not 0)

9. Are these equations direct variation? 2x + y = 0 -x + y = -1 4x - 5y = 0

10. Are these equations direct variation? 2x + y = 0 --> y = -2x --> YES -x + y = -1 --> y = x - 1 --> NO 4x - 5y = 0 --> y = 4 / 5 x --> YES

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12. Homework p256 #2-8 E, 11-22 C6, 58-62 E