(x²-1)(x²+3)=(x²+1)²+x

Question

(x²-1)(x²+3)=(x²+1)²+x

Answer 1

( x^{2}-1)( x^{2}+3)=( x^{2} +1)^2+x
x^4+3x^2-x^2-3=x^4+x^2+x^2+1+x
2x^2-3=2x^2+1+x
-x=1+3
x= -4.x