Factorise 2x^3 -5x ^2 -19 x + 42
Answers
Answered by
1
Answer:
The first step is to take out the
common factor
of 2x
⇒
2
x
(
x
2
+
x
−
42
)
...
...
.
.
(
A
)
Now factorise the
quadratic
inside the bracket.
Using the a-c method, find the factors of - 42 which sum to +1
These are +7 and - 6
⇒
x
2
+
x
−
42
=
(
x
+
7
)
(
x
−
6
)
substituting these into (A) gives the factorised form.
⇒
2
x
3
+
2
x
2
−
84
x
=
2
x
(
x
+
7
)
(
x
−
6
)
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