Answer:x=−4,x=0,x=5
Explanation:
take out a common factor of
x
2
f
(
x
)
=
x
2
(
x
2
−
x
−
20
)
the factors of - 20 which sum to - 1 are - 5 and + 4
⇒
f
(
x
)
=
x
2
(
x
−
5
)
(
x
+
4
)
to find zeros set
f
(
x
)
=
0
⇒
x
2
(
x
−
5
)
(
x
+
4
)
=
0
equate each factor to zero and solve for x
x
2
=
0
⇒
x
=
0
with multiplicity 2
x
−
5
=
0
⇒
x
=
5
x
+
4
=
0
⇒
x
=
−
4take out a common factor of
x
2
f
(
x
)
=
x
2
(
x
2
−
x
−
20
)
the factors of - 20 which sum to - 1 are - 5 and + 4
⇒
f
(
x
)
=
x
2
(
x
−
5
)
(
x
+
4
)
to find zeros set
f
(
x
)
=
0
⇒
x
2
(
x
−
5
)
(
x
+
4
)
=
0
equate each factor to zero and solve for x
x
2
=
0
⇒
x
=
0
with multiplicity 2
x
−
5
=
0
⇒
x
=
5
x
+
4
=
0
⇒
x
=
−
4