Looking at the graph, it appears that x = 7 is an x-intercept. If that is true, that would mean x − 7 is a factor. So, test x − 7 using the factor theorem.
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Just because it looks like x = 7 is an x-intercept, doesn’t mean that it is. Maybe the x-intercept is very close to 7 (like 7.001)—you would not be able to tell this from the graph. As a result, you must test what might be a factor using the factor theorem.
In this case you have determined that x − 7 is a factor. Isabel needs to perform the following division to determine another factor:
That is going to be a lot of work. Fortunately, there is a faster, mathematically equivalent process, called synthetic division. Watch Synthetic Division to see how the process works.
Complete questions 4.a., 4.b., and 4.c. on page 124 of the textbook.
Back to Isabel and the whooping cranes. Previously it was determined that x − 7 is a factor of −x4 + 12x3 − 37x2 + 6x + 56. Use long division or synthetic division, whichever you prefer, to determine another factor. Continue factoring until you have written −x4 + 12x3 − 37x2 + 6x + 56 as the product of four binomial factors.
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