derivitive of rational function: missing a negative

[rragas]

I have to find the derivitive of

y= (x^2 + 3x) / (7 - 2x)

I solved it like this
=
(7+2x)(2x+3)-(x^2+3x)(2)
______________________
(7+2x)^2

=
2x^2+14x+21
____________
(7+2x)^2

I have an answer sheet that tells me that I'm missing a negative. Their answer is:

21+14x-2x^2
___________
(7-2x)^2

I've looked over it several times, but i can't find the negative

 

[galactus]

I have to find the derivitive of

y= (x^2 + 3x) / (7 - 2x)

I solved it like this
=
(7+2x)(2x+3)-(x^2+3x)(-2)<--right here
______________________
(7+2x)^2

=
2x^2+14x+21
____________
(7+2x)^2

I have an answer sheet that tells me that I'm missing a negative. Their answer is:

21+14x-2x^2
___________
(7-2x)^2

I've looked over it several times, but i can't find the negative