I checked the answer by multiplying
Check:
(x 1 5) (x 2 6)
the two factors.
5 (x 1 5)x 2 (x 1 5)6
2
5 x
1 5x 2 6x 2 30
2
5 x
2 x 2 30
2
First I divided each term by the
18x
2 50
b)
common factor, 2. This left a
2
5 2(9x
2 25)
difference of squares.
2
I took the square root of
9x
and 25
5 2(3x 1 5) (3x 2 5)
to get
3x
and 5, respectively.
2
This is a trinomial of the form
c)
10x
2 x 2 3
2
ax
1 bx 1 c,
where
a 2 1,
and it has
no common factor.
I used decomposition by finding two
2
5 10x
1 5x 2 6x 2 3
numbers whose sum is
and whose
21
product is
These
(10) (23) 5 230.
numbers are 5 and
I used them to
26.
“decompose” the middle term.
I factored the group consisting of the
5 5x(2x 1 1) 2 3(2x 1 1)
first two terms and the group
consisting of the last two terms by
dividing each group by its common
factor.
I divided out the common factor of
5 (2x 1 1) (5x 2 3)
2x 1 1 from each term.
I noticed that the first and last terms
2
d)
9x
1 30x 1 25
are perfect squares. The square roots
are
3x
and 5, respectively. The middle
2
5 (3x 1 5)
term is double the product of the two
square roots,
2(3x) (5) 5 30x.
So this
trinomial is a perfect square, namely,
the square of a binomial.
2
Trinomials of this form may be
e) 2x
1 x 1 3
factored by decomposition. I tried to
come up with two integers whose
sum is 1 and whose product is 6.
There were no such integers, so the
trinomial cannot be factored.
100
2.3 Factoring Polynomials