In the expression 2a + 3b - a + 4, what are the like terms?

• A. 2a and -a
• B. 3b and 4
• C. All terms are like terms
• D. None of these

Answer: (A)

In the expression 2a + 3b - a + 4, like terms are defined as terms that contain the same variable raised to the same power. Here, the terms can be examined individually:

• 2a and -a both contain the variable 'a'. These terms can be combined because they are like terms.

• 3b is a term that contains the variable 'b' and cannot be combined with either of the 'a' terms.

• 4 is a constant term and does not share variables with 'a' or 'b', so it also does not combine with the 'a' or 'b' terms.

Thus, the correct answer indicates that 2a and -a are indeed like terms, which can be combined together. This demonstrates a fundamental principle of algebra, where only terms with the same variable can be combined in simplification processes.