Answer:√(x+3)+6=9
minus 6 both sides
√(x+3)=3
squar both sides
x+3=+/-9
minus 3 both sides
x=6 or -12
sub to see
√(6+3)+6=9
√(9)+6=9
3+6=9
9=9
true
other one
√(-12+9)+6=9
√(-9)+6=9
false (means this is an extranious answer)
x=6 and it is not extranious
D
72 is anres
or
X=6 not extraneous