Posted by Blake on Sunday, December 30, 2012 at 2:13pm.
A boy throws a stone into a lake from a 74 foot high wall. The chart gives the horizontal distance, x (in feet), the rock has traveled from Jesse and the height, y (in feet) of the rock above the lake.
Distance, x: (14) (24) (41) (55)
Height, y: (86.43) (91.36) (92.19) (85.75)
Write the equation that best fits the path of the rock from Jesse to the lake below.
I wasn't at school when we were taught this and the notes I have mention nothing of this. I am completely lost, can someone help?

Math  Reiny, Sunday, December 30, 2012 at 5:49pm
I will assume you want your data to fit an equation of the type
y = ax^2 + bx + c
from the first "point" (14,86.43)
86.43 = 196a + 14b + c , (#1)
from the 2nd:
91.36 = 576a + 24b + c , (#2)
from the 3rd:
92.19 = 1681a + 41b + c , (#3)
#2  #1:
4.93 = 380a + 10b #4
#3  #2
.83 = 1105a + 17b  #5
#4 times 17 > 83.81 = 6460a + 170b
#5 times 10 > 8.3 = 11050a + 170b
subtract them
75.51 = 4590a
a = .01645
in #4:
4.93 = 380(.01645) + 10b
b = 1.11814
in #1
86.43 = 196(.01645) + 14(1.11814) + c
c = 74
y = .1645x^2 + 1.11814x + 74
testing for point not used:
(55,85.75)
RS = .01645(55^2) + 1.11814(55) + 74
= 85.73
the given data was 85.74 , not bad
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