Final answer:
In the expression given, x2, 4x2, and 16x2 are like terms, and when combined they simplify to 21x2 because they share the same base and exponent.
Step-by-step explanation:
In the expression, x2 + 4x2 + 16x2, the terms x2, 4x2, and 16x2 are examples of like terms because they all have the same variable raised to the same power. Like Terms can be combined by performing addition or subtraction on their coefficients. In this case, you would add up the coefficients (1, 4, and 16) and then rewrite the expression as 21x2 because they are all coefficients of the term with x squared.
This simplification follows the rule that when you raise a number to an exponent, you're using it as shorthand for repeated multiplication, and like terms can only be combined if they have the same base and exponent.