math
posted by ppppp .
find the x intercepts of a parabola whenthe vertex is at 2,13 and y intercept at 0,5

the generic equations of parabola is:
y=ax^2+bx+c
by information of the vertex 2;13 i have two facts:
i) 13=a*2^2+b*2+c ....replacing(2;13)
ii)the director of the vertex as equation:
x=b/2a
by information "intercept at 0,5 ":
iii)5=a*0^2+b*0+c ....replacing(0;5)
tre equation tre unknowns a,b,c
you solve the system 
i forgot to specify in ii) x=b/(2a) => 2=b/(2a)