QUADRATIC WORD PROBLEMS

ALGEBRA UNIT 10 - SOLVING QUADRATIC EQUATIONS

SOLVING QUADRATICS BY FACTORING (DAY 1)

0

35

r

12

r

2

=

+

-

HOW TO SOLVE QUADRATIC EQUATIONS:

Step 1: Write equation in Standard Form.

Step 2:Factor the quadratic equation.

Step 3: After the problem has been factored we will complete a step called the T chart. Create a T separating the two ( ).

Step 4: Once ( ) are separated, set each ( ) = to 0 and solve for the variable.

Step 5:Check each of the roots in the ORIGINAL quadratic equation.

a

ac

b

b

x

2

4

2

-

-

=

1. Find the roots:

a

ac

b

b

x

2

4

2

-

-

=

2.Solve for y:

0

24

y

11

y

2

=

+

+

3. Find the zeroes:

0

6

x

5

x

2

=

-

-

4. Solve for y:

28

y

3

y

2

=

-

5.Find the roots:

30

x

x

2

+

=

6. Find the zeros:

35

w

5

2

=

7. A plot of land for sale has a width of x ft., and a length that is 8ft less than its width. A farmer will only purchase the land if it measures 240 square feet. What value of x will cause the farmer to purchase the land?

8.The length of a rectangle is 5 inches more than twice a number. The width is 4 inches less than the same number. If the area of the rectangle is 15, find the number

QUADRATIC WORD PROBLEM (DAY 2)

CONSECUTIVE INTEGERS/GEOMETRIC PROBLEMS

Review of Consecutive Integers Let Statements:

Consecutive Integers:

Consecutive Even Integers:

Consecutive Odd Integers:

1.Find two consecutive odd integers whose product is 99.

2. A certain number added to its square is 30. Find the number.

3.The square of a number exceeds the number by 72. Find the number.

4.Find two consecutive positive integers such that the square of the first decreased by 17 equals 4 times the second.

5.The ages of three family children can be expressed as consecutive integers. The square of the age of the youngest child is 4 more than eight times the age of the oldest child. Find the ages of the three children.

6.The altitude of a triangle is 5 less than its base. The area of the triangle is 42 square inches. Find its base and altitude

7.The length of a rectangle exceeds its width by 4 inches. Find the dimensions of the rectangle if its area is 96 square inches.

8.If the measure of one side of a square is increased by 2 centimeters and the measure of the adjacent side is decreased by 2 centimeters, the area of the resulting rectangle is 32 square centimeters. Find the measure of one side of the square (the original figure).

SOLVING QUADRATICS THAT CANT BE FACTORED

OPTION 1: COMPLETING THE SQUARE (DAY 3)

1) What is a quadratic equation?

2) What are the zeros (roots) of a quadratic equation? (algebraically and graphically)

3) What are some methods you know of to find the roots of a quadratic equation?

4) Factor:

16

x

8

x

2

+

+

5)

16

x

8

x

2

+

+

is an example of a perfect square trinomial. Explain why.

Procedure for Completing the Square

2x2 12x + 14 = 0

1. Rearrange the equation:

Get terms with variables on the left hand side.

Get c# by itself on the right hand side

2. If a# > 1 then divide through by a#.

3.

Identify the b#

(half it - square it - add it to both sides)

(This will form a perfect square trinomial)

4.

Write Expression as a perfect square trinomial

Simplify the # on the other side

5.

Square root both sides

Put a

on the right in front of term

6. Solve for x to find the roots.

Solve each quadratic equation by completing the square; express each root in simplest radical form.

1)

12

x

2

x

2

=

-

2)

4

5

y

3

y

2

2

=

-

+

3)

2

r

6

r

2

1

2

=

-

4)

0

24

x

6

x

3

2

=

-

+

5)

11

x

24

x

4

2

+

=

-

6)

0

5

x

4

x

4

2

=

-

-

COMPLETING THE SQUARE CONT (DAY 4)

Recall basic steps:

1) Solve

0

4

x

12

x

2

2

=

+

-

by completing the square; express the result in simplest form.

2)Brian correctly used a method of completing the square to solve the equation x

2

+ 7x 11 = 0. Brians first step was to rewrite the equation as x

2

+ 7x = 11. He then added a number to both sides of the equation. Which number did he add?

1)

2

7

2)

4

49

3)

2

49

4) 49

3)If x2 + 2 = 6x is solved by completing the square, an intermediate step would be

(1) (x + 3)2 = 7

(2) (x 3)2 = 7

(3) (x 3)2 = 11

(4) (x 6)2 = 34

4)The senior class at Bay High School buys jerseys to wear to the football games. The cost of the jerseys can be modeled by the equation C=0

, where C is the amount it costs to buy x jerseys. How many jerseys can they purchase for $430?

5)Collin is building a deck on the back of his house. He has enough lumber for the deck to be 144 square feet. The length should be 10 feet more than its width. What should the dimensions of the deck be?

6)The product of two consecutive negative odd integers is 483. Find the integers.

7)Solve

8

p

3

p

2

=

-

by completing the square.

SOLVING QUADRATICS THAT CANT BE FACTORED

OPTION 2: QUADRATIC FORMULA (DAY 5)

Recap:Solve

0

4

p

12

p

7

2

=

+

-

by completing the square

Completing the square and factoring are not always the best method to use when solving a quadratic as illustrated above.

To DERIVE a new method to solve a quadratic we go back to the beginning.

QUADRATIC FORMULA

To remember formula sing/hum the phase below to the pop goes the weasel song

x =s negative b, plus or minus the square root of b2 minus 4 a c, all over 2 a

******WRITE THE FORMULA DOWN AS YOU SING THE SONG******

Solve the following using the quadratic formula, answers should be in simplest radical form when possible.

1) Solve for x: x2 12x = -20

2)Solve for x: 2x2 + 9x = 18

Quadratic Formula:

3) Solve for x: x2 5x 3 = 0

4) Solve for x:2x2 4x = 1

5) Solve for x:5x2 2 = 3x

QUADRATIC FORMULA CONTINUED (DAY 6)

Quadratic Formula:

What is the quadratic formula used for?

Give some reason(s) to use the quad formula instead of completing the square method.

Solve the following using the quadratic formula. Answer should be in simplest radical form when possible.

1) Solve for x:-3x

2

= 8x 12

2) Solve for x: 3x2 + 5x 12 = 0

3)The Demon Drop at Cedar Point in Ohio takes riders to the top of a tower and drops them 60 feet. A function that approximates this ride is h= -16t

2

+ 64t + 60, where h is the height in feet and t is the time in seconds. About how many seconds does it take for riders to drop 60 feet (to the nearest tenth)?

4) Solve the following quadratic equation, x

2

= -7x 5, selecting a method that we learned, and state why you chose that method.

METHODS OF FINDING ROOTS (ZEROS) OF QUADRATIC EQUATIONS (DAY 7)

METHOD

REASON TO USE THIS METHOD

QUICK PROCEDURE

Find the roots by FACTORING:

1) x2 12x = -27

2) 2x2 + 3 = -7x

Find the roots by FACTORING:

3) x2 64 = 0

4)

x

x

15

5

2

=

Solve the equation using the QUADRATIC FORMULA, leave answers in simplest radical form.

5)x2 5x 3 = 2

6)

50

4

x

3

x

2

=

-

+

Find the roots by COMPLETING THE SQUARE, leave answers in simplest radical form.

9)3x2 - 2x 4 = 0

10)

0

2

5

2

2

=

+

-

x

x

Quadratic Equation (Standard Form):

EMBED Equation.3

Steps for using the Quadratic Formula: (Use when quad equation = 0)

Get equation equal to ZERO!!!

Put Equation in standard form: __________________________

Identify the a, b, and c #s.

Plug into the formula and simplify.

Created by K.Snyder

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