We now study a special type of function
Consider 1. f ( x ) = 7x3
- 4x2 + 3x
- 1
2. f ( x ) = ½ x + 5/2 x + 1
3. f ( y ) = 4y2 + Ö3y
- 1
4. f ( y ) = y½ - 4y2
+ y + 3
5. f ( z ) = z-2 + 5z + 1
Observations:
i) Indices of x and y in (1), (2) and (3) are
positive integers or Zero.
ii) Indices of y and z in (4) and (5) are negative
and fraction.
First three expressions or functions are polynomials
whereas forth and fifth are not polynomials.
At this stage, we restrict our study of polynomials
as a special type of
function whose domain is a set of reals.
Definition:
Ifare real
numbers and n is zero and positive integer then the function P is given
by is
called a " polynomial in x over reals " .
Note :(I)
are called coefficients.
(II) There are ( n + 1 ) terms in (1)
(III) If
then (1) becomes
which is a constant. Such polynomials are called constant polynomials.
For examples, p ( x ) = 5, p ( x ) = 3/2
etc.
(IV) If all coefficients including a constant
are zero. Then the polynomial is called ‘ zero ’ polynomial.
A polynomial with only one term is a monomial.
A polynomial with two terms is a binomial.
A polynomial with three terms is a trinomial.
(V) Usually polynomial is written in descending
order of its powers of variable say x. ( standard form ).
(VI) The degree of a polynomial is the
exponent in the term with the highest power.
For example, x5 + 7x3
- 3x + 2 has degree 5.
2x4 + 3x3 -
3 has degree 3.
3m2 + 4m - 1 has degree 2.
x - 2 has degree 1
Now consider a constant polynomial p ( x ) = 7 = 7x0
whose degree is ‘ 0 ’.
We do not define the degree of 0 i.e. zero
polynomial.
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