Question 1081255
Calculate the first difference by subtracting,
{{{d[1]=a[2]-a[1]=-3-(-1)=-3+1=-2}}}
{{{d[2]=a[3]-a[2]}}}
{{{d[3]=a[4]-a[3]}}}
{{{d[4]=a[5]-a[4]}}}
Do the same for the remaining numbers.
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Then calculate the second difference.
{{{D[1]=d[2]-d[1]}}}
{{{D[2]=d[3]-d[2]}}}
{{{D[3]=d[4]-d[3]}}}
If all the second differences are equal, the series is quadratic.
Else it is not.