Answer:
 
Step-by-step explanation:
Given : from the graph vertex is (5,3)
Also graph passes through point (8,12)
We use vertex form of quadratic equation
General vertex form is 

vertex is (5,3)
h= 5 and k =3
So equation becomes 
Now we need to find out 'a'
We use (8,12) to find out 'a'
Plug in x=8 and y = 12
 
 
12= 9a + 3
subtract 3 on both sides
9 = 9a
divide both sides by 9
so a=1
Final equation is 
 