Show that the tangent to P: ax^2 + bx + c with gradient m has a y intercept of c - ( (m - b)^2 / 4a )
OK so far my working would be...
find dydx to find gradient of tangent
dydx = 2ax + b
y intercept means x = 0, so when x =0, 2ax + b = b
From here i am stuck.
Any ideas would be appreciated