Answer:
[tex]x=\pm \sqrt{\frac{y-c}{a}}[/tex]
Step-by-step explanation:
[tex]y=ax^2 + c \\ \\ ax^2 =y-c \\ \\ x^2=\frac{y-c}{a} \\ \\ x=\pm \sqrt{\frac{y-c}{a}}[/tex]