SOLUTION: The cables between the two posts onthe Golden Gate Bridge is in the shape of a parabola. The bridge is 535 feet tall from the road to the top of the support poles and 4100 feet wi

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Question 1205668: The cables between the two posts onthe Golden Gate Bridge is in the shape of a parabola. The bridge is 535 feet
tall from the road to the top of the support poles and 4100 feet wide. Create an equation in standard and factored form to
represent the shape of the parobola
First write an equation in factored from

Found 2 solutions by MathLover1, ikleyn:
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
The standard form of a parabola:
y=ax%5E2+%2B+bx+%2B+c+
given:
height is h=535ft (which is y value of the vertex)
width is 4100ft
if we place the origin in the midpoint, then we have x=4100ft%2F2=2050ft from each side of the origin
than, the vertex is at (0,535) and x-intercepts are at (-2050,0) and (2050,0)

y=ax%5E2+%2B+bx+%2B+c....plug in x=0, y=535
535=a%2A0%5E2+%2B+b%2A0+%2B+c
c=535


plug in x=2050, y=0
0=a%2A2050%5E2+%2B+b%2A2050+%2B+535
4202500+a+%2B+2050+b+%2B+535=0....solve for a
a+=-+2050b+%2F4202500-+535%2F4202500
a+=-b%2F2050-107%2F840500....eq.1


plug in x=-2050, y=0
0=a%2A%28-2050%29%5E2+%2B+b%2A%28-2050+%29%2B+535
-4202500+a+%2B+2050+b+-+535+=+0....solve for a
2050+b+-+535+=+4202500+a
a+=2050b+%2F4202500-+535%2F4202500
a+=b%2F2050-107%2F840500....eq.2

from eq.1 and eq.2 we have
-b%2F2050-107%2F840500=b%2F2050-107%2F840500
-b%2F2050=b%2F2050
b=0


go to
a+=b%2F2050-107%2F840500....eq.2, substitute+b
a+=0%2F2050-107%2F840500
a+=-107%2F840500

your equation is:

y=-%28107%2F840500%29x%5E2+%2B+535


The factored form of a parabola:
y+=+a%28x+-+p%29%28x+-+q%29, where p and q+are the x-intercepts of the parabola
substitute x-intercepts

y+=+-%28107%2F840500%29%28x+-+2050%29%28x+-+%28-2050%29%29
y+=+-%28107%2F840500%29%28x+-+2050%29%28x+%2B2050%29



Answer by ikleyn(52777) About Me  (Show Source):