G.MATH
POLYNOMIALS AND THEIR ZEROS AMC
Polynomials 1999 AHSME #17

Let  be a polynomial which when divided by x - 19 has the remainder 99, and when divided by x – 99 has remainder 19. What is the remainder when  is divided by (x – 19)(x – 99)?
VIDEO LECTURE


MAIN CONCEPTS
Employ the linear factor theorem.
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SOLUTION

This question can look intimidating on first sight but after some careful implementation of the various theorems, the answer pretty much falls in place.

We notice that (x – 19)(x – 99) is a quadratic polynomial. The remainder when this is divided into  will be linear, that is,

for some constants a and b.

If we were to put  and , the linear factor theorem implies that

Subtracting these equations an substituting gives

So a = -1 and b = 99 - (-1)19 =118. The remainder is therefore – x + 118.

All information presentated, less questions and exercises, is original content of Donny, with slight references to various books.
Video courtesy of YouTube.com service.
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