1. Lesson 8-7 Quadratic Variation Objectives: Students will: Be able to find equations of direct, inverse, and joint quadratic variation Solving problems involving quadratic variation

2. Quadratic Variation 3 possibilities 1) Direct→y = kx 2 “y varies directly with the square of x” 2) Inverse → “y varies inversely with the square of x” 3) Joint →y = kxz “y varies jointly with x and z” Or Combos of these!!

3. Writing Variation Equations 1)Choose equation 2)Plug in values 3)Solve for k 4)Re-write equation with k-value

4. Example 1 Find the equation of variation where y varies inversely as the square of x, and y = 2 when x = 3. so

5. Example 2 Find an equation of variation where y varies jointly as x and z, and y = 2, when x = 3, and z = 4.

6. Example 3 The intensity I of the light from a lamp varies directly as the wattage W of the lamp and inversely as the square of the distance D from the lamp. The intensity is 10 units when a 100-watt bulb is used at a distance of 20 feet. What is the intensity if a 75-watt bulb is used at 25 feet.

7. Example 4 The force of attraction F between two magnets varies inversely as the square of the distance D between them. The force is 5 newtons when the magnets are 2 cm apart. What is the force when the magnets are 5 cm apart?

8. Assignment 8-7/370-371/1-15o, 25, 31,33