Final answer:
The expression √-49 is indeed equal to 7i because the square root of a negative number involves the imaginary unit 'i'.
Step-by-step explanation:
The student asked about the expression √-49 and self-answered that it is equivalent to 7i. This is a mathematics question dealing with complex numbers. The square root of a negative number results in an imaginary number. The square root of -49 is 7 multiplied by the imaginary unit 'i', where 'i' is the square root of -1. Hence, the student's answer of 7i is correct.