· Letters represent an unknown or generic real number

· Sometimes with restrictions, such as a member of a certain set, or the set of values that makes an equation true.

·
Often a letter from the end of the alphabet: *x*, *y*,
*z*

·
Or a letter that stands for a physical quantity: *d*
for distance, *t* for time, etc.

· Fixed values, like 2 or 7.

·
Can also be represented by letters: *a*, *b*,
*c*, *p*, *e*, *k*

*Terms* are Separated by + or –

*Factors* are multiplied together.

Coefficients are constant factors that multiply a variable or powers of a variable

The middle term has 2 factors, –3 and *x.* We say that the coefficient
of *x* is –3.

The first term has three factors, 2 and two factors of *x.* We say that
2 is the coefficient of *x*^{2}.

The last term is a factor all by itself (although the number 4 could be factored into 2 ´ 2).