Section 9.5Quadratic Formula – Round 2

Goal: Use the quadratic formula to solve quadratic equations and to find

the x-intercepts.

Knocking out math problems

one by one!

Algebra 1(B)Daily Warm Up

Sketch a graph of the function.

y = -3x² + 6x + 2

1. Does graph open up or down?

2. Give coordinates of the vertex.

3. Write the of the axis of symmetry.

down

(1, -5)

x = 1

<Fill In The Blanks>

• From yesterday’s lesson …

Step 1:

Step 2:

Step 3:

Step 4:

The “ “ Formula

Homework Questions?

Connections

Section 9.4 Section 9.5

• Solve by using the quadratic formula: 2 12 0x x

• Represent the solution graphically: 2 12 0x x

So … What Have We Learned?

The quadratic formula allows us to find the solutions to a quadratic equation

ANDthese are also the x-intercepts.

Step-by-Step Guide

How do we find the x-intercepts of y = x² + 3x – 8?

Step 1: Write in standard form.

x² + 3x – 8 = 0

Step 2: Identify a, b, c.

a = 1, b = 3, c = -8

Step 3: Plug into quadratic formula.

2 4

2

b b acx

a

≈ 1.70, ≈ -4.70 3 41

2

3 41

2

KENTUCKY DERBY

You will be split into groups of 4. Each member of the group is

responsible for showing his/her own work.

A letter will be assigned to each person in the group.

Letters will be called randomly. That person will have to show a teacher his/her answer.

Your horse will advance to the next square if you are correct.

The first horse to cross the finish line is the winner.

Directions

KENTUCKY DERBY

Solve by using the quadratic formula.

Problem 1

Start Finish

x = 1, x = -7

KENTUCKY DERBY

Solve by using the quadratic formula.

Problem 2

Start Finish

x = 8, x = -2

KENTUCKY DERBY

Solve by using the quadratic formula.

Problem 3

Start Finish

x = 1.5, x = 2

KENTUCKY DERBY

Solve by using the quadratic formula.

Problem 4

Start Finish

x = -0.6, x = -1

KENTUCKY DERBY

Solve by using the quadratic formula.

Problem 5

Start Finish

x = 0.47, x = -6.47

Homework

pgs. 536-537 #44-46, 53-55

Quiz 9.4-9.6 on Monday 4/6!