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Explore how to find formulas for general terms using finite differences in sequences. Learn to identify linear, quadratic, and cubic patterns and apply them to solve for unknown constants. Practice with examples to master the concept.
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Finite differences • When given a sequence that is neither arithmetic nor geometric, we can try to find finite differences. • For example: • 2, 5, 10, 18, 30, 47, 70,…
Finite differences • If the first difference is constant, our terms are linear (an arithmetic sequence) • If the second difference is constant, our formula for general terms is quadratic • If the third difference is constant, our formula for general terms is cubic. • Generalize the formula, plug in known values, and solve the system for the unknown constants.
Example • Find a formula for the nth term • 3, 5, 8, 12, 17, 23, …
Example • Find • 1, 7, 15, 25, 37, 51, …
Homework • Pg642 #45-59 odd