State how many imaginary and real zeros the function has.

f(x) = x5 + 7x4 + 2x3 + 14x2 + x + 7

A3 imaginary; 2 real
B4 imaginary; 1 real
C0 imaginary; 5 real
D2 imaginary; 3 real

Verified Answer :

Answer:

B. 4 imaginary; 1 real

Step-by-step explanation:

Given the polynomial:

x^5 + 7x^4 + 2x^3 + 14x^2 + x + 7

it can be reordered as follows

(x^5 + 2x^3 + x ) + (7x^4  + 14x^2 + 7)

Taking greatest common factor at each parenthesis

x(x^4 + 2x^2 + 1) + 7(x^4  + 2x^2 + 1)

Taking again the greatest common factor

(x + 7)(x^4 + 2x^2 + 1)

Replacing x^2 = y in the second parenthesis

(x + 7)(y^2 + 2y + 1)

(x + 7)(y + 1)^2

Coming back to x variable

(x + 7)(x^2 + 1)^2

There are two options to find the roots

(x + 7) = 0

or

(x^2 + 1)^2 = 0 which is the same that (x^2 + 1) = 0

In the former case, x = -7 is the real root.  In the latter, (x^2 + 1) = 0 has no real solution. Therefore, there is only 1 real root in the polynomial.