X^2+6x+m=0
Move the variables to the right-hand side by adding their opposites to both sides
x^2+6x+m-x^2-6x=0-x^2-6x
Since two opposites add up to 0 , remove them from the expression
6x+m-6x=0-x^2-6x
M=0-x^2-6x
Removing 0 doesn't change the value, so remove it from the expression
The Solution is:
M=-x^2-6x