Quadratic 呀~~help me!!!

a)
Since one of the x-intercept is 6 and the y-intercept is 12
by putting (6,0) and (0,12) into y=a(x-h)^2-(25/2)
we have:
a(6-h)^2=25/2---(1)
ah^2=49/2---(2)
(1)/(2):
[(6-h)/h]^2=25/49
(6-h)/h=5/7 or (6-h)/h=-5/7
h=7/2 or h=21
by putting h=7/2 and h=21 into (2)
on solving , the solutions are (a=2, h=7/2) or (a=1/18, h=21)
b)
for a=2, h=7/2
y=2(x-(7/2))^2-(25/2)
set y=0,
(x-(7/2))^2=25/4
x-(7/2)=5/2 or x-(7/2)=-5/2
x=6 (rejected) or x=1
for a=1/18, h=21
y=(1/18)(x-21)^2-(25/2)
set y=0,
(x-21)^2=225
x-21=15 or x-21=-15
x=36 or x=6 (rejected)
Hence , the other x-intercepts of the graph are 1 and 36.