X(x+9)=0
x=?
what does x have to be for the answer to be 0?

when we solve the equation it will become
x² + 9x= 0
now here a = 1 , b = 9 and c = 0 
by using quaderatic formula
x = -b +,-√b ²- 4ac / 2a     ( 2a is divided by all terms )
by putting values
x = - 9 +,- √81 / 2(1)               ( √81 = 9)
x = -9 + 9 / 2    and x = -9 -9 /2
x = 0                and x = -18 /2 = -9  
now there are two values for x one is- 9 and other is 0 
so we put -9 as the value of x then answer will be zero..