2 ways
zero product property
easy way
zero product
factor perfect square
m^2-3^2=0
(m-3)(m+3)=0
set each to zero
m-3=0
x=3
m+3=0
m=-3
m=-3 or 3
easy way
add 9 to both sides
m^2=9
sqrt both sides remember to take postive and negative roots
m=+/-3
m=-3 or 3
B is answer
