Answer:
No, it isn't.
Explanation:
In (-9, 8), -9 is the x coordinate. The y is 8. In order for -9 to have been a solution, the y would have had to been -9.
Here's what I mean:
(The graph I drew is in the image. I hope it makes sense! Sorry for my bad handwriting, I'm not used to writing on computers.)
I hope this helps!
-No one