Page 134 - Math Course 2 (Book 1)

Factoring: Trinomials

c is Negative
Your Turn!

Example b and c are Positive

2
2
Factor x + 3x – 18. Factor x + 3x + 2.
A. (x + 3)(x + 1)
In this trinomial, b = 3 and c = –18. This means B. (x + 2)(x + 1)
m + n is positive and mn is negative, so either m C. (x – 2)(x – 1)
or n is negative, but not both. Therefore, make a D. (x + 1)(x + 1)
list of the factors of –18 where one factor of each
pair is negative. Look for the pair of factors with a Answer
sum of 3.

Factors of –18 Sum of Factors

1, –18 –17
b is Negative and c is Positive
–1, 18 17
2
2, –9 –7 Factor x – 10x + 16.
–2, 9 7 A. (x + 4)(x + 4)
3, –6 –3 The correct B. (x + 2)(x + 8)
factors are C. (x – 2)(x – 8)
–3, 6 3 –3 and 6. D. (x – 4)(x – 4)

2
x + 3x – 18 = (x + m)(x + n) Write the pattern.
Answer
= (x – 3)(x + 6)
Answer
m = –3 and n = 6
c is Negative

2
2
Factor x – x – 20. Factor x + 4x – 5.
A. (x + 5)(x – 1)
Since b = –1 and c = –20, m + n is negative and B. (x – 5)(x + 1)
mn is negative. So either m or n is negative, but not C. (x – 5)(x – 1)
both.
D. (x + 5)(x + 1)
Factors of –20 Sum of Factors
1, –20 –19 Answer
–1, 20 19
2, –10 –8
–2, 10 8
The correct
2
3, –5 –1 Factor x – 5x – 24.
factors are
–3, 5 1 4 and –5.
A. (x + 8)(x – 3)
B. (x – 8)(x – 3)
2
x – x – 20 = (x + m)(x + n) Write the pattern. C. (x + 8)(x + 3)
= (x + 4)(x – 5) m = 4 and n = –5
D. (x – 8)(x + 3)
Answer
Answer (x + 4)(x – 5)

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