1. Warm Up Use a calculator to evaluate
Warm Up Use a calculator to evaluate. Round the results to the nearest hundredth.
Practice 1
Practice 2
Practice 3

2. 9-4A Solving Quadratic Equations by Using the Quadratic Formula
You will need a calculator for today’s lesson.
Algebra Glencoe McGraw-Hill Linda Stamper

3. Today you will solve quadratic equations by using the
quadratic formula:
The quadratic formula is read as “x equals negative b, plus or minus the square root of b squared minus 4ac, all divided by 2a.”
The quadratic formula gives the solutions of ax2 + bx + c = 0 in terms of the coefficients a, b, and c.

4. Sing-a-long: Pop Goes the Weasel
x equals negative b,
plus or minus square root,
b squared minus 4ac,
all over 2a.”
Sing – a – long competition by rows.

5. The first step in using the quadratic formula is to identify the values of a, b, and c.
Write the equation in standard form. Identify values of a, b, and c.
Write problem.
Rewrite in standard form.
Identify values for a, b, and c.

6. Example 1 Write the equation in standard form
Example 1 Write the equation in standard form. Identify the values of a, b, and c.
Example 2 Write the equation in standard form. Identify the values of a, b, and c.

7. Solve the equation.
Identify values for a, b, c.
Write quadratic formula.

8. Solve . If the solution involves radicals, round to the nearest tenth.
Rewrite the equation in standard form.
Identify values for a, b, c.
Write quadratic formula.

9. Solve. If the solution involves radicals, round to the nearest tenth.
Example 3
Example 4
Example 5
Round in the last step!

10. Example 3 Solve . If the solution involves radicals, round to the nearest tenth.

11. Solve. If the solution involves radicals, round to the nearest tenth.
Example 4
Example 5

12. Homework
9-A12 Page #9-20,29–31,60-62.

13. Keystrokes for TI-30X IIS
Use a calculator to evaluate Round the results to the nearest hundredth. ( √ 1 + 2
2nd 3 ) ) ÷ 4 = ( 1 - 2
2nd √ 3 ) ) ÷ 4 =
When evaluating radical expressions that are not perfect squares, round the answer in the last step.
Keystrokes for TI-30X IIS
Does your calculator have order of operations?

14. Use a calculator to evaluate
Use a calculator to evaluate Round the results to the nearest hundredth. 1 + 2 X 3 √ = ÷ 4 = 1 - 2 X 3 √ = ÷ 4 =
When evaluating radical expressions that are not perfect squares, round the answer in the last step.
Keystrokes for TI-30X A

15. When using the quadratic formula, it is helpful to change the value under the radical to addition when simplifying.
Find the value of b2 – 4ac for the equation.
Write problem.
Identify the values for a, b and c.
Write the expression.
Simplify. (Place values in parentheses and change subtraction to addition to avoid sign errors.)

16. Example 3 Find the value of b2 – 4ac for the equation.