what is 3x+6y+9z

Answer 1

I think it may be helpful for you to review what a variables and equations mean.

x, y, and z are unknown values. For example, what if all you had was 3x? That means you have some amount of something (x), and however much you have of it, it comes in a multiple of 3. For a real world example, maybe you are buying candy bars. X could be the value of some candy bar, and having 3x candy bars means you are paying for 3 of them. The price of x could be anything-- the 3 just tells you that however much it is, you need to multiply that price by 3.

What about if you had 3x + 6y? That's like having 3 of one flavor and 6 of another. For example, x could be a chocolate bar and y could be caramel. So, whatever the price of x and y are (chocolate and caramel), we know you will pay 3 times whatever the price of chocolate plus 6 times the price of caramel. Chocolate and caramel are allowed to cost different amounts, because sometimes x and y can be different.

So, for 3x + 6y + 9z, you just add one more flavor. You have 3 chocolarte, 6 caramel, and 9 fruit flavor. And those prices (the values of x y and z) can be anything.

I don't know if you like real world examples like that, but hopefully it helps you understand the point. 3x + 6y + 9z doesn't have much meaning on its own. Its just a way of saying you have 3 values of things you dont know, but whatever those values are, the total thing you have (the price) can be calculated as 3 times the first thing, plus 6 times the second thing, plus 9 times the third thing.

Answer 2

Some short answers:

"3x+6y+9z"

This is an expression, which is a definition of some combination of constants and variable. An expression can be used in an equation.

OR: The given expression describes a vector in a 3-axis coordinate system