Respuestas
I. La coordenada faltante del foco:
1. (x+5)² = 20(y-10) ; F1 ( -5, ? )
Si, 4p = 20 ⇒ p = 5
h = -5
k = 10
k+p = 10+5 = 15
F1 (-5, 15 )
2. x² = 24y ; F2 ( 0, ? )
Si, 4p = 24 ⇒ p = 6
h = 0
k = 0
k+p = 0+6 = 6
F2 ( 0, 6)
3. (y+5)² = 60(x-10) ; F3 ( ?, -5 )
Si, 4p = 60 ⇒ p = 15
h = 10
k = -5
h+p = 10+15 = 25
F3 (25, -5)
4. (y-15)² = 80(x-15) ; F4 ( ?, 15 )
Si, 4p = 80 ⇒ p = 20
h = 15
k = 15
h+p = 15+20 = 35
F4 (35, 15)
II. La ecuación de la parábola correspondiente a cada V, F:
Sabiendo que,
(x-h)²=4p(y-k) siendo V(h, k) y F(h, k±p) ;
(y-k)²=4p(x-h) siendo V(h, k) y F(h±p, k) ;
• V(-2, 3) ; F(-2, 4)
Si, h = -2; k= 3 ; k+p=4
p = 4 - 3 = 1
(x + 2)²= 4(y-3)
• V(-3, 1) ; F(0, 1)
Si, h = -3; k= 1 ; h-p=0
p = 3
(y-1)²= 12(x+3)
• V(1, 2) ; F(1, -1)
Si, h = 1 ; k = 2 ; k+p=-1
p= -1-2 = -3
(x - 1)²= -12(y-2)
• V(2, -3) ; F(2, -4)
Si, h = 2 ; k = -3 ; k-p=-4
p= -4+3 = -1
(x - 2)²= -4(y+3)
• V(3, -1) ; F(0, -1)
Si, h = 3; k= -1 ; h+p=0
p = -3
(y+1)²= -12(x-3)
• V(-1, -2) ; F(-1, 1)
Si, h = -1 ; k = -2 ; k+p=1
p= 1+2 = 3
(x + 1)²= 12(y+2)