What is x to the third plus 3x plus 5x plus 15?

Answer 1

x3 + 3x + 5x + 15

That's a third-degree expression in 'x'.

It can be cleaned up a little bit, by adding the 3x and the 5x. Doing that

doesn't change anything; it only makes the expression neater:

x3 + 8x + 15

Now it's a third-degree trinomial in 'x'. If anybody wants to know what number

the expression is equal to, they'll have to tell you what number 'x' is first. The

value of the whole expression depends on the value of 'x', and every time 'x'

changes, the value of the expression changes.

Notice that it's not an equation, it doesn't ask any question, and it has no

solution or 'answer'. It's just a number, the value of which can be anything.