Question

Which of the following is the complete list of roots for the polynomial function f(x)=(x^2+6x+8)(x^2+6x+13)

Answer 1

Answer:

x = -4 or x = -2

Step-by-step explanation:

$f(x)=(x^2+6x+8)(x^2+6x+13)\\\\f(x)=0\iff(x^2+6x+8)(x^2+6x+13)=0\iff\\x^2+6x+8=0\vee x^2+6x+13=0\\\\x^2+6x+8=0\\x^2+4x+2x+8=0\\x(x+4)+2(x+4)=0\\(x+4)(x+2)=0\iff x+4=0\ \vee\ x+2=0\\x+4=0\qquad\text{subtract 4 from both sides}\\\boxed{x=-4}\\x+2=0\qquad\text{subtract 2 from both sides}\\\boxed{x=-2}\\\\x^2+6x+13=0\qquad\text{subtract 13 from both sides}\\x^2+6x=-13\\x^2+2(x)(3)=-13\qquad\text{add}\ 3^2=9\ \text{to both sides}\\x^2+2(x)(3)+3^2=-13+9\qquad\text{use}\ (a+b)^2=a^2+2ab+b^2\\(x+3)^2=-4$