need help

Well it has to be c, because the opening of the parabola is at the bottom, and that means a negative coefficient "a". The greater the absolute value of "a" in ax^2+bx+c the narrower the parabola. Changing the value of “b” will move the axis of symmetry of the parabola from side to side; increasing b will move the axis in the opposite direction. Changing the value of “c” will move the vertex of the parabola up or down and “c” is always the value of the y-intercept.

Thanks answer guest,

there is a double root at x=1

So the equation will be   y=a(x-1)(x-1)

Sub in another point like (0,-2)  to  find the value of a.     

As guest has already said, it is concave down so a will be negative.