Question

Tìm x :

(x²+2x+3)(x²+2x+5)=8

Answer 1

\(^{x^4}+4^x+12x^2+16x+15=8\\ x^4+4x^3+12x^2+16x+15-8=0\\ \left(x+1\right)\times\left(x^3+3x^2+9x+7\right)=0\\ \left(x+1\right)^2\times\left(x^2+2x+7\right)=0\\ \left(x+1\right)^2=0\\ x^2+2x+7=0\\ x=-1,x\notin R\)

Answer 2

=>(x^2+2x)^2+8(x^2+2x)+15=8

=>(x^2+2x)^2+8(x^2+2x)+7=0

=>(x^2+2x+7)(x^2+2x+1)=0

=>(x+1)^2=0

=>x=-1