Question

Solving quadratic equations with complex solutions x2 + 4x + 8 = 0.

Answer 1

Answer:

$\large\boxed{x=-2\pm2i}$

Step-by-step explanation:

$x^2+4x+8=0\qquad\text{subtract 8 from both sides}\\\\x^2+4x+8-8=0-8\\\\x^2+2(x)(2)=-8\qquad\text{add}\ 2^2\ \text{to both sides}\\\\x^2+2(x)(2)+2^2=-8+2^2\qquad\text{use}\ (a+b)^2=a^2+2ab+b^2\\\\(x+2)^2=-8+4\\\\(x+2)^2=-4\iff x+2=\pm\sqrt{-4}\\\\x+2=\pm\sqrt{(4)(-1)}\qquad\text{use}\ \sqrt{ab}=\sqrt{a}\cdot\sqrt{b}\\\\x+2=\pm\sqrt4\cdot\sqrt{-1}\qquad\text{use}\ \sqrt{-1}=i\\\\x+2=\pm2\cdot i\qquad\text{subtract 2 from both sides}\\\\x=-2\pm2i$