Let's go through each statement from the given expression $9x + 2y + 1$ and determine which are true:

1. "1 is a constant."

   • True: A constant is a number on its own without any variables, and here, $1$ is indeed a constant.

2. "9x is a coefficient."

   • False: In this case, $9x$ is a term, not a coefficient. The coefficient is $9$, while $x$ is the variable.

3. "9x + 2y + 1 is written as a sum of three terms."

   • True: The expression has three distinct terms: $9x$, $2y$, and $1$.

4. "9x and 1 are like terms."

   • False: Like terms must have the same variable part. $9x$ has the variable $x$, but $1$ has no variable, so they are not like terms.

5. "9x is a factor."

   • False: $9x$ is not a factor; it is a term in the expression.

6. "None of these are true."

   • False: As seen, at least two of the statements are true.

Summary of the true statements:

• 1 is a constant.
• $9x + 2y + 1$ is written as a sum of three terms.

Would you like further clarification on any of these points or more detailed explanations?

Related Questions:

1. What is a coefficient in algebraic terms?
2. How do you identify like terms in an expression?
3. What does it mean when terms are considered factors in an expression?
4. Can a constant term ever be a factor in an algebraic expression?
5. How do you simplify an expression with multiple terms?

Tip:

When identifying like terms, focus on the variable parts. Only terms with exactly the same variable and exponents can be combined as like terms.