已知抛物线y=-1/2x²-(n+1)x-2n(n

已知抛物线y=-1/2x²-(n+1)x-2n(n
已知抛物线y=-1/2x²-(n+1)x-2n(n

已知抛物线y=-1/2x²-(n+1)x-2n(n
y=-1/2(x^2+2(n+1)x+4n)=-1/2(x+2)*(x+2n)=0
x1=-2,x2=-2n
故A坐标是(-2,0)B(-2n,0),D(0,-2n)
S(ABD)=1/2|X2-X1|*|Yd|=12
(-2n+2)*(-2n)=24
4n^2-4n-24=0
n^2-n-6=0
(n-3)(n+2)=0
n=3,n=-2
n<0,故有n=-2
故解析式是y=-x^2/2+x+4