SOLUTION: Find a polynomial of degree 4 that has zeros -3, 2, -2 and -1 and with the coefficient of x^2 is -3.

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Find a polynomial of degree 4 that has zeros -3, 2, -2 and -1 and with the coefficient of x^2 is -3.      Log On


   



Question 1056898: Find a polynomial of degree 4 that has zeros -3, 2, -2 and -1 and with the coefficient of x^2 is -3.
Found 2 solutions by Boreal, math_helper:
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
The factors for -3,-2,2, and -1 are
(x+3)(x^2-4)(x+1)=x^4+4x^3-x^2-16x-12
Now multiply everything by 3 which will not change the roots but will make the coefficient of x^2 -3.
3x^4+12x^3-3x^2-48x-36
graph%28300%2C300%2C-10%2C10%2C-100%2C20%2C3x%5E4%2B12x%5E3-3x%5E2-48x-36%29

Answer by math_helper(2461) About Me  (Show Source):
You can put this solution on YOUR website!
General form of a 4th degree polynomial is:
ax%5E4+%2B+bx%5E3+%2B+cx%5E2+%2B+dx+%2B+e++=+0+
This can be constructed from the zeros:

The zero at -3 means there is a factor (x+3) (because plugging in x=-3 gives zero)
The zeros at 2,-2, and -1 yield three more factors: (x-2)(x+2) and (x+1), respectively.
Putting all the factors together:
(x+3)(x-2)(x+2)(x+1)
= (x+3)(x+1)(x+2)(x-2) (reordered, will multiply first two, last two next)
= %28x%5E2%2B4x%2B3%29%2A%28x%5E2-4%29
= x%5E4%2B4x%5E3%2B3x%5E2-4x%5E2-16x-12
= x%5E4%2B4x%5E3-x%5E2-16x-12
The problem said the coefficient of x%5E2 should be -3, since it is already -1, we need to multiply the polynomial by 3:
Ans: 3x%5E4%2B12x%5E3-3x%5E2-48x-36