Solve Each Equation by Graphing.

4. x^2-10+21=0

5. 4x^2+4x+1=0

6. x^2+x-6=0

7. x^2+2x+3=0

8. -x^2-6x-9=0

9. x^2-6x+5=0

10. x^2+2x+3=0

11. x^2-3x-10=0

12. -x^2-8x-16=0