Slide 2:
direct variation – a function with the form y = ax, where a is a nonzero constant.
a is called the constant of variation.
y varies directly with x.
EX y = 5x
y = -6x
Slide 3:
EX Tell whether the equation represents a direct variation. If so, identify the constant of variation. -3 - -3 -2x -2x The constant of variation is 2/3. +x +x This is not a direct variation.
Slide 4:
The y-intercept in a direct variation is always 0.
Slide 5:
EX Graph y = -3x. y = -3x + 0
Slide 6:
EX The distance that you travel at a constant speed varies directly with the time spent traveling. It takes you 2 hours to travel 100 miles.
let d = distance
t = time
d = rt
100 = r(2)
100 = 2r 2 2 50 = r Your speed is 50 mph. d = 50t is the direct variation.