Question

What is the solution of the set?

Answer 1

`x^2=16-4x\ \ \ |+4x\\\\x^2+4x=16\ \ \ \ |+2^2\\\\\underbrace{x^2+2\cdot x\cdot2+2^2}_((a+b)^2=a^2+2ab+b^2)=16+2^2\\\\(x+2)^2=20\iff x+2=\pm√(20)\\\\x+2=-√(4\cdot5)\ \vee\ x+2=√(4\cdot5)\ \ \ |-2\\\\x=-2-2\sqrt5\ \vee\ x=-2+2\sqrt5`

Answer: D.