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Mathematics 6 Online
OpenStudy (anonymous):

.

OpenStudy (anonymous):

@campbell_st

OpenStudy (campbell_st):

for this type of question I always use the general form \[(x - h)^2 = 4a(y - k)\] the vertex is (h, k) and the focal length is a so start by finding the focal length... the distance between the directrx and focus on the line of symmetry is souble the focal length so how far between y = -2 and y = 6...?

OpenStudy (anonymous):

4?

OpenStudy (anonymous):

No 8

OpenStudy (anonymous):

My bad, I did it wrong

OpenStudy (campbell_st):

can you just check the directrixx is y = -2 and focus is (2, 6)

OpenStudy (campbell_st):

great, 8 is correct... so to find the value of a, just ahlve the answer you has for the distance between the focus and directrix...

OpenStudy (campbell_st):

thedirectrix is below the focus... so the parabola is concave up... and the vertex is a units below the focus on the line of symmetry x = 2 so the vertex is (2, 6 - a)

OpenStudy (anonymous):

Kinda confused, do I need to subtract something?

OpenStudy (campbell_st):

ok... you need to find a, based on the information 2a = 8 the disatnce between y = -2 and y = 6 so what is the value of a..?

OpenStudy (anonymous):

4

OpenStudy (campbell_st):

great the vertexx of the parabola is a units below the focus on the line x = 2 so the vertex is (2, 6 - a) using your value of a, what is the vertex..?

OpenStudy (campbell_st):

|dw:1416960918629:dw|If I draw a simple plot of the info I know the parbola is concave up

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