 What is the difference between Expression and Equation in Algebra
EXPRESSION:
An expression contains numbers and letters (named as variables), but NOTÂ an equal sign.
For instance, 3n + 2 is an expression.
There are two terms in this expression.
3n is one term
The other term is 2
The letter n is called the variable because it can have different values.
The co-efficient of n is 3 because it is the number that multiplies the variable.
3n means 3 × n
EXAMPLE 1:
Ahmad is x years old. Saima is 4 years older than Ahmad. Write down an expression for Saima's age.
SOLUTION:
As Saima is 4 years older than Ahmad, so add 4 to x.
Thus, Saima is x + 4 years old.
EXAMPLE 2:Â
Find the value of expression 2a - 5b when a = 2 and b = 4
SOLUTION:
SubstituteÂ
2 for aÂ
andÂ
4 for bÂ
in the expression 2a - 5b
2 × 2 - 5 × 4
= 4 - 20
= -16
Thus, the value of expression 2a - 5b when a = 2 and b = 4 is -16.
Equivalent Expressions:
Expressions that look different but work the same are called equivalent expressions.Â
For example, all the expressions below are equivalent expressions.
5t + 6
6 + 5tÂ
5 × t + 6Â
EQUATION:
An equation contains numbers and letters (named as unknowns) AND an equal sign.
For instance, 3n + 2 = 5 is an equation.
Here, n is the unknown
3 is the co-efficient of n
and the numbers 2 and 5 are constants.Â
Example:
Solve the equation:
x - 3 = 4
For solving the equation, our mission is to isolate the unknown at left or right side of an equal sign.
Here, x is the unknown and 3 is subtracted from x.
Add 3 to both sides of equal sign.
x - 3 + 3 = 4 + 3
As, - 3 + 3 = 0, so only x remains at left side of equation. Thus, above equation reduces to
x = 7
Thus, x = 7 is the solution or root of equation x - 3 = 4
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Solved examples on how to construct an EXPRESSION
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