Question 1188217: I haven't done this before. I'm so confused. N=3 -2 and 8+5i are zeros. F(2)=244. Says find the nth degree polynomial function with real coefficients satisfying the given conditions.
Found 3 solutions by math_helper, MathTherapy, ikleyn: Answer by math_helper(2461) (Show Source):
You can put this solution on YOUR website!
Apply these two rules:
1. Each zero b contributes a factor (x-b)
2. Complex zeros (and roots) always come in conjugate pairs
The zero at 3 contributes (x-3)
The zero at -2 contributes (x-(-2)) = (x+2)
The zero at 8+5i and conjugate contribute (x-8-5i)(x-8+5i)
Multiply all four of these factors, and simplify, to get:
But, this function has g(2) = -244, and the problem states f(2)=244,
thus we need to multiply g(x) by -1, and the final answer is:
Note that f(x) is just g(x) flipped across the x-axis (mirror image).
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EDIT 12/1 -- I see (now, after seeing MathTherapy's answer) that the intention was to indicate N=3 as the _DEGREE_ of the polynomial. I interpreted N=3 as one of the zeros. Thanks MathTherapy for catching that.
Answer by MathTherapy(10552) (Show Source):
You can put this solution on YOUR website! I haven't done this before. I'm so confused. N=3 -2 and 8+5i are zeros. F(2)=244. Says find the nth degree polynomial function with real coefficients satisfying the given conditions.
N = 3 indicates that there are 3 zeroes, or 3 solutions. One of the 3 zeroes or solutions is - 2, and the other 2 are:
8 + 5i, and its CONJUGATE, 8 - 5i.
With the 3 zeroes/solutions being - 2, 8 + 5i, and 8 - 5i, it follows that, x = - 2, x = 8 + 5i, and x = 8 - 5i, thus
making the function’s factors: x + 2, x - 8 - 5i, and x - 8 + 5i.
We now have the following function: f(x) = a(x + 2)(x - 8 - 5i)(x - 8 + 5i), which then becomes:
y = a(x + 2)[(x - 8)2 - (5i)2] ------ FOILing/Expanding (x - 8 - 5i)(x - 8 + 5i)
-------- Substituting f(2) = 244, or (2, 244) for (x, y) to determine value of “a”
With ”a” being 1,
This is your 3rd degree polynomial, or a polynomial with N = 3, and the given roots.
Answer by ikleyn(52794) (Show Source):
You can put this solution on YOUR website! .
I agree with the solution by @MathTherapy.
N = 3 means that the degree of a polynomial is 3.
So, this " 3 " is not a root: it is the degree of the polynomial.
Notice to the visitor: it is entirely YOUR FAULT
presenting the problem in an inaccurate and ambiguous way.
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