y=ax^2+bx+c=a[x+(b/2a)]^2+(4ac-b^2)/(4a)=a(x-1)^2+4
B(3,0)
0=a(3-1)^2+4,-b/(2a)=1,(4ac-b^2)/(4a)=4
a=-1,b=2,c=3
y=-x^2+2x+3
A(-1,0),B(3,0),D(0,3)
T[e,(3-e^2+2e)],M(e,0)
k(MN)=k(BD)=-1
MN:y=-x+e
-x+e=-x^2+2x+3
x^2+3x+e-3=0
xN= ,yN=
|MN|= ,|MD|= ,BD=3√2
|MD|^2=|MN|*|BD|
e=,
T( )