# Expressions Involving Variables, Substitution Assignment Help ## Introduction to Expression involving variables, Substitution:

Variable A symbol, usually a letter of the alphabet, such as the letter n, that is used to represent a number. An expression, such as n 5, that consists of one or more numbers and variables along with one or more arithmetic operations are Variable expression. An algebraic expression can consist of one or more numbers and variables along with one or more arithmetic operations.

## Evaluate a Variable Expression

write the expression, substitute a number for each variable, and simplify the result.

For example: Evaluate expression n+3 when n = 4

Solution: given n = 4

Substituting n=4 in expression n+3

n+3 =4+3

=7

### Substitution:

When we replace letters in an expression or equation with number, this process is called Substitution.

For example: How can 4+3* be written as an algebraic expression?

Using n for the variable we can write this as 4+3n

We can evaluate the expression 4+3n by substituting different values for n

When n=5 4+3n= 4+3*5

= 4+15

=19

When n= 11 4+3n = 4+3*11

=4+33

=37

### The Method of Substitution:

 Method Type of System Substitution Linear or nonlinear, two variables Graphical method Linear or nonlinear, two variables Elimination Linear, two variables Gaussian elimination Linear, three or more variables 