Transforming quadratics

Question

Has a vertex of v(2,-9) and goes through a(-1,9). Put equation in standard form

 

 

I don't know what the a(-1,9) means

Answer 1

y=a(x-h)^2+k with vertex (h,k)

vertex=(2,-9)

y=a(x-2)^2-9

goes through point (-1,9)

9=a(-1-2)^2-9

9=a(-3)^2-9

9=a(9)-9

9+9=a(9)

18=a(9)

a=18/9

a=2

y=2(x-2)^2-9 is the equation in vertex form

y=2(x^2-4x+4)-9

y=2x^2-8x+8-9

y=2x^2-8x-1