Download Key Concepts Sect 2.3 Direct Variation: A linear function defined by

Key Concepts Sect 2.3
Direct Variation: A linear function defined by the equation y = kx where k ≠ 0.
Constant of Variation: The value of k in the equation y = kx.
Guided Practice Sect 2.3
Ex 1: For each function, determine whether y varies directly with x. If so, find the constant of variation and the equation.
b.)
a.)
x
y x
y ­1 3 7
14 2 ­6 9 18 5 15 ­4 ­8 Ex 2: For each function, tell whether y varies directly with x. If so, find the constant of variation.
b.) 5x = ­2y
a.) 3y = 7x + 7
Guided Practice Sect 2.3
Ex 3: The perimeter of a square varies directly as the length of a side of a square. The formula P = 4s relates the perimeter to the length of a side.
a.) Find the constant of variation.
b.) Find how long a side of the square must be for the perimeter to be 64 cm.
Ex 4: Suppose y varies directly with x and y = 15 when x = 27. Find y when x = 18.
Sect 2.3: p.74
Homework
3­21 every 3rd, 23, 24­51
every 3rd, 52