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How can you tell that the student made an error when factoring? Explain the error.

Factor:
6x²-x-12
6x²9x + 8x - 12
3x(2x-3)-4(-2x +3)

1 Answer

2 votes

Explanation:

For a polynomial of the form

a

x

2

+

b

x

+

c

, rewrite the middle term as a sum of two terms whose product is

a

c

=

6

12

=

72

and whose sum is

b

=

1

.

1

out of

x

.

6

x

2

(

x

)

12

Rewrite

1

as

8

plus

9

6

x

2

+

(

8

9

)

x

12

Apply the distributive property.

6

x

2

+

8

x

9

x

12

Factor out the greatest common factor from each group.

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2

x

(

3

x

+

4

)

3

(

3

x

+

4

)

Factor the polynomial by factoring out the greatest common factor,

3

x

+

4

.

(

3

x

+

4

)

(

2

x

3

)

User Matthew Heusser
by
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