SOLUTION: 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 condition

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: 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 condition      Log On


   



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) About Me  (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:
+g%28x%29+=+x%5E4-17x%5E3%2B99x%5E2%2B7x-534

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:
+f%28x%29+=+-%28x%5E4-17x%5E3%2B99x%5E2%2B7x-534%29+
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) About Me  (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)
    matrix%281%2C3%2C+y%2C+%22=%22%2C+a%28x+%2B+2%29%28%28x+-+8%29%5E2++-++25i%5E2%29%29 
    matrix%281%2C3%2C+y%2C+%22=%22%2C+a%28x+%2B+2%29%28%28x+-+8%29%5E2++-++25%28-+1%29%29%29 
  matrix%281%2C3%2C+244%2C+%22=%22%2C+a%282+%2B+2%29%28%282+-+8%29%5E2+%2B+25%29%29 -------- 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) About Me  (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.