y=ax^2+bx+c
25a-5b+c=0.(1)
a-b+c=0.(2)
(1)-(2):
24a-4b=0
b=6a
c=5a
-(4ac-b^2)/(4a)=|2|
a=0.5,-0.5
b=3,-3
c=2.5,-2.5
y=0.5x^2+3x+2.5
y=-0.5x^2-3x-2.5