SOLUTION: Find the nth-degree polynomial function with real coefficients satisfying the given conditions: n=4; -3; 1/4, 2i are zero f(-2)=-144

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Question 1055571: Find the nth-degree polynomial function with real coefficients satisfying the given conditions: n=4; -3; 1/4, 2i are zero f(-2)=-144

Answer by ikleyn(52776) About Me  (Show Source):
You can put this solution on YOUR website!
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Find the nth-degree polynomial function with real coefficients satisfying the given conditions:
n=4; -3; 1/4, 2i are highlight%28cross%28zero%29%29 zeroes and f(-2)=-144.
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A polynomial of the degree 4 with real coefficients and the roots -3, 1%2F4, 2i is

f(x) = a%2A%28x-%28-3%29%29%2A%28x-%281%2F4%29%29%2A%28x-2i%29%2A%28x%2B2i%29 = 4a%2A%28x%2B3%29%2A%284x-1%29%2A%28x%5E2%2B4%29.     (1)


where "a" is the real number, a leading coefficient.

To find the value of "a", use the condition f(-2) = -144.

Substitute x= -2 into the polynomial (1). You will get

f(-2) = 4a%2A%28-2%2B3%29%2A%284%2A%28-2%29-1%29%2A%28%28-2%29%5E2%2B4%29 = 4a%2A1%2A%28-9%29%2A8 = -288a.

Thus  -288a = -144.  Hence,  a = %28-144%29%2F%28-288%29 = 0.5.

Finally, the polynomial is

f(x) = 0.5%2A%28x%2B3%29%2A%284x-1%29%2A%28x%5E2%2B4%29.