Question

(oﾟ▽ﾟ)o

請問第8題怎麼算

8.試求過點4(1,6)且與拋物線-8x= 2+4y+28共軸,共焦點的拋物線方程式為何?
(有兩解)
& 右圖為一拋物線的部分圖形,1準線為 L: x='-3,0
y
AP(1717)

Answer 1

imma_idiot

4(-2(x +3)) =(y+2)² → 焦點(-2 -3, -2) =(-5, -2), 軸 y +2 =0;
令 F =4(a(x -(-5 -a))) =(y+2)², 過(1, 6) → 4a(a +6) =64, a =2 or -8
帶回得 F := (y+2)² =8(x +7) or (y+2)² =-32(x -3).

應該是這樣 (吧

(oﾟ▽ﾟ)o

算式有點不太懂😅
從假設那邊開始😵‍💫