Question

Suppose the least-squares regression line for a set of data has slope 72.4. now suppose we remove a point from the data, compute the least-squares regression line, and find that the new slope is 8.7. the point removed would be considered

Answer 1

...an outlier.

However, this may or may not be an outlier, depending on the nature of the data. A details on the detection of outliers may be found in an NIST article on outlier detection.