Question

giải phương trình sau:

(x+2)(x+4)(x+6)(x+8)+16=0

Answer 1

Lời giải:
PT \(\Leftrightarrow [(x+2)(x+8)][(x+4)(x+6)]+16=0\)

\(\Leftrightarrow (x^2+10x+16)(x^2+10x+24)+16=0\)

\(\Leftrightarrow a(a+8)+16=0\) (đặt \(x^2+10x+16=a)\)

\(\Leftrightarrow (a+4)^2=0\Rightarrow a+4=0\)

\(\Leftrightarrow x^2+10x+20=0\)

\(\Leftrightarrow (x+5)^2=5\Rightarrow x=\pm \sqrt{5}-5\)

Vậy.........