An expression with one term is called a monomial. For example, [tex]\( -5abc \)[/tex] or [tex]\( 2(x+y) \)[/tex] are monomials.

An expression with two terms is called a binomial. For example, [tex]\( 15xy - 5abc \)[/tex] or [tex]\( 2(x+y) - 4ab \)[/tex] are binomials.

An expression with three terms is called a trinomial. For example, [tex]\( -ab + 15abc - cd \)[/tex] is a trinomial.

### Example
Simplify:
a) [tex]\( 3a + 2b - 6a + 4b^2 - b + 2a \)[/tex]

Solution:
First, write the like terms next to each other:
[tex]\[ 3a - 6a + 2a + 2b - b + 4b^2 \][/tex]

Then, add or subtract the like terms:
[tex]\[ (3a - 6a + 2a) + (2b - b) + 4b^2 = -a + b + 4b^2 \][/tex]

b) [tex]\( 7a + 12b - a^2 \)[/tex]

Solution:
You cannot simplify this expression because there are no like terms.

### EXERCISE 8.1
1. Which of these expressions are polynomials? If the expression is a polynomial, describe the polynomial by the number of terms it has.
a) [tex]\( -13x^2y + 52y \)[/tex]
b) [tex]\( 2a^2 - 3b^2 + 16 \)[/tex]
c) [tex]\( y + y^2 + 12 \)[/tex]
d) [tex]\( -\frac{1}{2}xyz^3 \)[/tex]



Answer :

Let's analyze each given expression to determine whether it is a polynomial and, if it is, to categorize it by the number of terms it has.

### Expression a) [tex]\(-13 x^2 y + 52 y\)[/tex]

1. Is it a polynomial?
To determine if this is a polynomial, we need to check if each term consists of variables raised to non-negative integer exponents and whether it involves only addition, subtraction, or multiplication.
- The first term is [tex]\(-13 x^2 y\)[/tex], where [tex]\(x\)[/tex] is raised to the power of 2 and [tex]\(y\)[/tex] is raised to the power of 1.
- The second term is [tex]\(52 y\)[/tex], where [tex]\(y\)[/tex] is raised to the power of 1.

Both terms meet the criteria of a polynomial.

2. Number of terms?
This expression has two terms: [tex]\(-13 x^2 y\)[/tex] and [tex]\(52 y\)[/tex]. So, it is a binomial.

### Expression b) [tex]\(2 a^2 - 3 b^2 + 16\)[/tex]

1. Is it a polynomial?
- The first term is [tex]\(2 a^2\)[/tex], where [tex]\(a\)[/tex] is raised to the power of 2 (a non-negative integer).
- The second term is [tex]\(-3 b^2\)[/tex], where [tex]\(b\)[/tex] is raised to the power of 2.
- The third term is [tex]\(16\)[/tex], which is a constant term.

Since all terms meet the criteria of a polynomial, this expression is a polynomial.

2. Number of terms?
This expression has three terms: [tex]\(2 a^2\)[/tex], [tex]\(-3 b^2\)[/tex], and [tex]\(16\)[/tex]. So, it is a trinomial.

### Expression c) [tex]\(y + y^2 + 12\)[/tex]

1. Is it a polynomial?
- The first term is [tex]\(y\)[/tex], where [tex]\(y\)[/tex] is raised to the power of 1.
- The second term is [tex]\(y^2\)[/tex], where [tex]\(y\)[/tex] is raised to the power of 2.
- The third term is [tex]\(12\)[/tex], which is a constant term.

Since all terms meet the criteria of a polynomial, this expression is a polynomial.

2. Number of terms?
This expression has three terms: [tex]\(y\)[/tex], [tex]\(y^2\)[/tex], and [tex]\(12\)[/tex]. So, it is a trinomial.

### Expression d) [tex]\(-\frac{1}{2} x y z^3\)[/tex]

1. Is it a polynomial?
This expression involves a term [tex]\(-\frac{1}{2} x y z^3\)[/tex], which might initially appear to be a polynomial term because it consists of variables [tex]\(x\)[/tex], [tex]\(y\)[/tex], and [tex]\(z\)[/tex] raised to integer powers. However, the coefficient is a fraction [tex]\(-\frac{1}{2}\)[/tex].

In polynomials, the coefficients are allowed to be any real numbers, including fractions. Hence, this expression still meets the criteria of a polynomial.

2. Number of terms?
This expression has only one term: [tex]\(-\frac{1}{2} x y z^3\)[/tex]. So, it is a monomial.

### Summary:
- a) [tex]\(-13 x^2 y + 52 y\)[/tex] is a polynomial and is a binomial.
- b) [tex]\(2 a^2 - 3 b^2 + 16\)[/tex] is a polynomial and is a trinomial.
- c) [tex]\(y + y^2 + 12\)[/tex] is a polynomial and is a trinomial.
- d) [tex]\(-\frac{1}{2} x y z^3\)[/tex] is a polynomial and is a monomial.