72
82
An equation if both expressions are equal
That means that the two expressions represent the same number.
equivalent
72
82
Equivalent expressions.
the answer is a(n) equationequationWhen two expressions are equivalent they can form an equation.
equivalent expressions
A statement that equates two equivalent expressions is called an Identity.
4b-b
85
An equation if both expressions are equal
In the same way that you would solve equations because equivalent expressions are in effect equations
That means that the two expressions represent the same number.
If you mean (9x-8y)(9x+8y) then it is 81x^2 minus 64y^2