Question 384088
In a general expression, x represents any number.


To solve for a specific number, you replace x with that number in the equation.


example:


y = x^2 + 3*x - 5


If you want to know the value of y when x = 3, you replace x with 3 in the equation to get:


y = 3^2 + 3*3 - 5 = 9 + 9 - 5 = 18 - 5 = 13


When you get into functional notation (if not already), then you will see:


f(x) = x^2 + 3*x - 5


When x = 3, then you will see:


f(3) = 3^2 + 3*3 - 5


The 3 replaces the x to give you the value of the equation when x = 3.


If you want to know the value of y or f(x), when x = 5, then you replace x with 5, etc.