The function is .
If is a rational zero, then
is a factor of
and
is a factor of
.
Here, and
.
Write the possible value of in simplest form.
and
.
Make a table and test some possible rational zeroes:
\![]() | \
![]() | \
![]() | \
![]() | \
![]() | \
![]() | \
![]() | \
![]() | \
![]() | \
![]() | \
![]() | \
![]() | \
Observe the table:
\Since , there is a zero at
.
The depressed polynomial is .
The quadratic function is .
(Quadratic formula)
(Substitute
and
)
(Simplify)
(Add and simplify)
and
(Separate two roots)
and
(Simplify)
The three real roots are ,
and
.
The zeroes of the functions are and
.