Answer:
x can be 3, -3, i, or -i.
Step-by-step explanation:
If you can't find the factoring by looking at this, simplify the equation.
let
x
2
=
y
to make things easier to see
Now we have
y
2
−
8
y
−
9
=
0
See it now?
We can factor into
(
y
−
9
)
(
y
+
1
)
Now substitute back in
x
2
for
y
.
(
x
2
−
9
)
(
x
2
+
1
)
Since
(
x
2
−
9
)
is a difference of two squares,
(
x
−
3
)
(
x
+
3
)
Now we have
(
x
−
3
)
(
x
+
3
)
(
x
2
+
1
)
x can be 3, -3 for the first two parts
x
2
+
1
=
0
can become
x
2
=
−
1
Taking the positive and negative root means
x
=
±
√
−
1
Thus
x
=
±
i
in addition to 3 and -3.
