Factor the Trinomial Completely $m ^ { 2 } - 4 m - 21$

Multiple Choice

Factor the trinomial completely. $m ^ { 2 } - 4 m - 21$

A) $( m - 7 ) ( m - 3 )$
B) $( m + 7 ) ( m - 3 )$
C) $( m - 7 ) ( m + 3 )$
D) $( m + 7 ) ( m + 3 )$
E) not factorable