what is the equation of this graph?

Answer:
y = x³ +2x² +x -1
Step-by-step explanation:
The attachment shows the four points we can read from the graph and the cubic regression function that fits them.
y = x³ +2x² +x -1
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Additional comment
It is useful to become familiar with the regression function capability of your graphing calculator or spreadsheet. Free or inexpensive apps are available for tablet or phone, and on the web.