Question 149195
1) x/x+xy
=y
is this correct? NO
To combine, both terms need to have the same denominator.
x/x + xy
= x/x + x^2y/x
= (x+x^2y)/x
= [x(1+xy)]/x
= 1+xy
.
2)3x^2+6x/3x^2+9x
=6/9=2/3 is this correct? NO
I'll assume your original problem is:
(3x^2+6x)/(3x^2+9x)  (correct me if I'm wrong)
Now, you "factor" the numerator and denominator to get:
[3x(x+2)]/[3x(x+3)]
= (x+2)/(x+3)
.
3)x^2+2x+1/x+1
I'll assume your original problem is:
(x^2+2x+1)/(x+1)
Factoring the numerator we get:
[(x+1)(x+1)]/(x+1)
= x+1
.
4)x^2+3x-18/2x-6
I'll assume your original problem is:
(x^2+3x-18)/(2x-6)
Factoring we get:
[(x-3)(x+6)]/[2(x-3)]
= x+6
.
5)2x^2-4x-6/x-3 
I'll assume your original problem is:
(2x^2-4x-6)/(x-3)
= [2(x^2-2x-3)]/(x-3)
= [2(x-3)(x+1)]/(x-3)
= 2(x+1)