How can you find the value of 'a' in a quadratic function (y=ax+bx+c) when given one co-ordinate of the x intercept and the y intercept?

Question

hartnn · Answer

what are the intercepts and point given ?

hartnn · Answer

ok, let me give you an example : 
if x -intercept is 2,0 and y-intercept is 0,4 
so, we have 
f(x) = ax^2 + bx +c 
to get y-intercept you put x = 0 
so, 
y-intercept = f(0) = 0+0+c = c
so, c= 4 

to get x intercept, put f(x) =0 
ax^2+bx +4 = 0
also, since we know that 2,0 lies on f(x), we can put x=2 
4a+2b +4= 0 
you need some more info to get 'a'
are both x-intercepts given ? or only one ?