Lesson 4.2B

Review Graph y = -4x2 + 8x + 2 vertex (1,6) y-intercept (0,2)

Let’s try to graph y = (x – 8)(x – 2). Where does this graph cross the x-axis? x = 8 and x = 2 What is the x-coordinate of the vertex? x = 5 What are the coordinates of the vertex? (5,-9) What is the y-intercept? (0,16)

Graphing Quadratics in Intercept Form Intercept form y = a(x – p)(x – q) The x-intercepts are p and q. The vertex is (p+q, ?) 2 The y-intercept is (0,?)

Practice 1. y = (x – 3)(x – 7) x-int(s) (3,0) (7,0) vertex (5,-4) y-int (0,21) 2. y = 2(x + 3)(x – 1) x-int(s) (-3,0) (1,0) vertex (-1,-8) y-int (0,-6) 3. y = -(x + 1)(x – 5) x-int(s) (-1,0) (5,0) vertex (2,9) y-int (0,5)

One last problem… Graph y = 2x(x + 4) What form is this?

Looking ahead… 1. (x + 4)(x + 3) = 2. (x – 5)(x + 1) =

Review y = (x – 2)2 – 3 y = x2 + 4x + 5 y = 2(x – 1)(x + 5)

Does y = 2(x + 5)2 – 8 have a maximum or minimum value? What is it?

Applications The height h of a volleyball t seconds after being hit is h = -16t2 + 48t + 4. What is the maximum height of the volleyball? From what height was the volleyball hit?