ATAR Notes: Forum
VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: sailinginwater on October 09, 2018, 07:31:25 pm
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Why is multiple choice 3 C and not A?
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If the graph of a polynomial has an x-intercept at x = n, then (x – n) is a factor of the polynomial. This is true for any value of n.
For that question, since the x-intercepts of the graph are at x = b, x = c, x = d, then the polynomial has factors (x – b), (x – c), (x – d).
Many students incorrectly chose option A because they reasoned that if b is a negative number, then (x + b) is a factor (thinking that you need to "flip the sign"). This is not correct. If you substitute in x = b into the factor, you should get 0. But if you substitute x = b into (x + b), you'll get 2b, not 0. Hence (x + b) is not a factor.
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If the graph of a polynomial has an x-intercept at x = n, then (x – n) is a factor of the polynomial. This is true for any value of n.
For that question, since the x-intercepts of the graph are at x = b, x = c, x = d, then the polynomial has factors (x – b), (x – c), (x – d).
Many students incorrectly chose option A because they reasoned that if b is a negative number, then (x + b) is a factor (thinking that you need to "flip the sign"). This is not correct. If you substitute in x = b into the factor, you should get 0. But if you substitute x = b into (x + b), you'll get 2b, not 0. Hence (x + b) is not a factor.
Thanks ;D
I just realised that a lot of the time the incorrect alternatives in multiple choice questions are common mistakes made?
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