The perimeter of a rectangle is 68 km. If the length is 2 km less than three times the width, w
1 answer:
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Answer:
1. A
2. D
3. D
Step-by-step explanation:
The standard form of a parabola is
..... (1)
Where, (h,k) is vertex, (h,k+p) is focus and y=k-p is directrix.
1. The directrix of a parabola is y=−8 . The focus of the parabola is (−2,−6) .
...(a)
.... (b)
On solving (a) and (b), we get k=-7 and p=1.
Put h=-2, k=-7 and p=1 in equation (1).
Therefore option A is correct.
2 The directrix of a parabola is the line y=5 . The focus of the parabola is (2,1) .
...(c)
.... (d)
On solving (c) and (d), we get k=3 and p=-2.
Put h=2, k=3 and p=-2 in equation (1).
Therefore option D is correct.
3. The focus of a parabola is (0,−2) . The directrix of the parabola is the line y=−3 .
...(e)
.... (f)
On solving (e) and (f), we get k=-2.5 and p=0.5.
Put h=0, k=-2.5 and p=0.5 in equation (1).
Therefore option D is correct.