SΔABC=1/2BC×3=9,
BC=6,
∴B(-2,0),C(4,0),
又A(1,3)或(1,-3),
设Y=a(X+2)(X-4)
⑴当A(1,3)时,
3=a×3×(-3),
a=-1/3,
∴Y=-1/3(X^2-2X-8)=-1/3X^2+2/3X+8/3.
⑵当A(1,-3)时,
-3=a×3×(-3),
a=1/3,
Y=1/3(X^2-2X-8)=1/3X^2-2/3X-8/3.