Answer:
[tex]x=1[/tex]
Step-by-step explanation:
Complete the square
[tex]f(x)=-3x^2+6x+7[/tex]
[tex]y=-3x^2+6x+7[/tex]
[tex]y-10=-3x^2+6+7-10[/tex]
[tex]y-10=-3x^2+6x-3[/tex]
[tex]y-10=-3(x^2-2x+1)[/tex]
[tex]y-10=-3(x-1)^2[/tex]
[tex]y=-3(x-1)^2+10[/tex]
Identify vertex and axis of symmetry
[tex]y=a(x-h)^2+k[/tex]
[tex](h,k)\rightarrow(1,10)[/tex]
[tex]x=h\rightarrow x=1[/tex]
