Answer:
−
344064
x
3
Explanation:
There's a quick way to answering questions like this without the need to go through the whole process of finding the terms before the
x
3
term:
Using the
n
C
r
button, the value of
n
represents the expansion power of
9
and the
r
would be the term you want to find, so in this case, it would be
3
.
Therefore, the coefficient of the general
x
3
term is:
9
C
3
=
84
However, you can only do this if the expansion is in the format of
(
1
+
x
)
n
.
To find the
x
3
coefficient for
(
4
−
x
)
9
:
(
a
+
x
)
n
=
a
n
+
n
a
n
−
1
x
+
(
n
(
n
−
1
)
2
!
)
a
n
−
2
x
2
+
(
n
(
n
−
1
)
(
n
−
2
)
3
!
)
a
n
−
3
x
3
+
...
...
+
x
n
Step-by-step explanation:
