I would just like a second opinion please to ensure I am doing this correctly.
When y = 0
0 = -x^2 + 4x + 5
- 5 = 4x
x = - 1.25
I understand the two roots and how you got them, but the formula has been modified.
- b + or - square root D / 2a
See the changes I have not seen before?
Capital D not squared, and - 4ac missing?
Like I said before this subject is new to me and is a new learning curve.
I don't think the formula has been modified.
In general if you have a quadratic equation:
Then this equation has:
two different solutions (or roots) if
If then the two identical solutions are:
There're no real solutions.
Is this clear? If you need a prove of this then you can ask it.