Answer:
A. m^2+7m+10=0
Step-by-step explanation:
This is a problem in pattern matching, and in substituting a variable for a pattern.
(x^2+3)^2 +7x^2 +21 = -10 . . . . . . given
(x^2 +3)^2 +7(x^2 +3) = -10 . . . . . factor the last two terms
m^2 +7m = -10 . . . . . . . . . . . . subsitute m for x^2 +3
m^2 +7m +10 = 0 . . . . . . . . add 10 to both sides; matches A
