Trend formula completely wrong

[Beleriand_K]

When I enter the following data into Excel and generates af Forecast Analysis with a Polynomial Trendline (Order 2) Excel shows an almost perfect trendline in the diagram. But when I choose Display equation on chart, it comes up with a Trend formula that has nothing to do with reality.

This is Excels Trendline formula:

Y = -0,0044x^2+0,6225x+13,408

If I put three of the numbers above into this formula, the results are this:

80 => 35,048 (real result in table: 13,88)
100 => 31,658 (real result in table: 24,53)
120 => 24,748 (real result in table: 31,63)

Apart from being very different from the results in the table, the Y-values gets smaller in the Trend formula, while they get bigger in the input table. So there seems to something fundamentally wrong with the equation.

I have searched the internet for an explanation, but without succes. The only answer I have found is, that I should use more decimals, but I have tried to extend the number of decimals to 30, and it doesn't help.

I suppose Excel is working as it should, so it must be me doing something wrong. Can anyone figure out, what it is? Because I surely can't.

80	13,88
81	14,54
82	15,18
83	15,80
84	16,41
85	17,01
86	17,59
87	18,16
88	18,72
89	19,29
90	19,79
91	20,31
92	20,82
93	21,32
94	21,81
95	22,29
96	22,75
97	23,21
98	23,66
99	24,10
100	24,53
101	24,95
102	25,36
103	25,77
104	26,17
105	26,56
106	26,94
107	27,31
108	24,68
109	28,04
110	28,40
111	28,75
112	29,09
113	29,43
114	29,76
115	30,08
116	30,40
117	30,72
118	31,03
119	31,33
120	31,63

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[shg]

You're welcome.