\
The expression is
, 
Intermediate value theorem :
\The function
is continuous on the closed interval
, let
be the number between
and
, where
then exist a number
in
such that
.
Prove that the number
exists between
and
such that
.
.
Substitute
in the function.

.
Substitute
in the function.

Thus,
.
The function
is continuous since it is a polynomial.
The intermediate value theorem states that there is
between
and
such that
.
\
The value
exists between
and
such that
.