Secant lines & average rate of change with arbitrary points (with simplification)

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Problem

A secant line intersects the curve y, equals, x, start superscript, 2, end superscript, minus, 3, x at two points with x-coordinates 5 and t, where t, does not equal, 5.
What is the slope of the secant line in terms of t ?
Your answer must be fully expanded and simplified.
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