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Mathematics 18 Online
OpenStudy (study.geek.123):

How do I do this?

OpenStudy (study.geek.123):

OpenStudy (adamaero):

Draw a picture

jimthompson5910 (jim_thompson5910):

Place the parabola so that it's vertex lies on the y axis. The dog will start at the point (2,0) since the start of the ramp is 2 ft from the peak of the ramp The vertex is at the point (0,6) because the peak is 6 ft at this point By symmetry, there's another point on this parabola and it is (-2,0) Use the three points: (2,0) (0,6) (-2,0) to determine the equation of the parabola

OpenStudy (study.geek.123):

tried that

OpenStudy (study.geek.123):

how do i make that into an equation though

jimthompson5910 (jim_thompson5910):

y = ax^2 + bx + c 6 = a(0)^2 + b(0) + c ... plug in (x,y) = (0,6) c = 6 y = ax^2 + bx + c 0 = a(2)^2 + b(2) + c ... plug in (x,y) = (2,0) 0 = 4a+2b+c 4a+2b+c = 0 4a+2b+6 = 0 ... plug in c = 6 This is the first equation y = ax^2 + bx + c 0 = a(-2)^2 + b(-2) + c ... plug in (x,y) = (-2,0) 0 = 4a-2b+c 4a-2b+c = 0 4a-2b+6 = 0 ... plug in c = 6 This is the second equation

jimthompson5910 (jim_thompson5910):

So you now have this system 4a+2b+6 = 0 4a-2b+6 = 0 add up the two equations to eliminate b. Then solve for 'a'

jimthompson5910 (jim_thompson5910):

Tell me what you get when you solve for 'a'

OpenStudy (study.geek.123):

2/3?

jimthompson5910 (jim_thompson5910):

incorrect

jimthompson5910 (jim_thompson5910):

adding up the two equations gives 8a+0b+12 = 0 8a+12 = 0 a = ???

OpenStudy (study.geek.123):

-2/3?

jimthompson5910 (jim_thompson5910):

you're dividing in the wrong order

jimthompson5910 (jim_thompson5910):

8a + 12 = 0 8a = -12 a = -12/8 a = -3/2 a = -1.5

jimthompson5910 (jim_thompson5910):

agreed?

OpenStudy (study.geek.123):

ohhh i divided wrong got it thx

jimthompson5910 (jim_thompson5910):

so we know a = -1.5 and c = 6. What is the value of b?

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