The function f is defined by f : 2x^2-12x + 13 for 0 <=x <=A, where A is a constant.
(i) Express f(x) in the form a(x + b)2 + c, where a, b and c are constants. [3]
(ii) State the value of A for which the graph of y = f(x) has a line of symmetry. [1]
(iii) When A has this value, find the range of f.
i)2x^2-12x + 13=a(x + b)^2 + c=ax^2+2abx+ab^2+c
2x"2=ax^2 so a=2
-12x=2abx=4bx so b=-3
13=ab^2+c=2*(-3)^2+c so c=-5
f(x)=2(x-3)^2-5
ii)A=6
iii)max value of f(x) is f(6)=13
range of f is [-5,13]