Polly wanna cracker?

Hi guys, i need help in understanding why my polynomial trendline appears this way. Furthermore, and not necessarily in this example,i sometimes use multi linear regression to find out a y value based on 3 x's, this value's are in a rage between 15-45 and it sometimes happens to return a value such as 965 or -320 which is impossible cause all my data is in between that range, i mean they're basketball teams and that is the number of field goals made.
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