What is the sum of all numbers a for which the graph of y=x^2+a and the graph of y=ax intersect one time?
y = x^2 + a
y = ax
Set these equal
x^2 + a = ax
x^2 - ax + a = 0
If they intersect once.....then there is only one root which means that the discriminant = 0
a^2 - 4a = 0 factor
a( a - 4) = 0
a = 0 or
a = 4
So....the sum is 4
