解:
原式=[2√(1+2x^2)-2x×2x/√(1+2x^2)]/(1+2x^2)
=[2√(1+2x^2)-4x^2√(1+2x^2)/(1+2x^2)]/(1+2x^2)
=[2(1+2x^2)√(1+2x^2)-4x^2√(1+2x^2]/(1+2x^2)^2
=[2√(1+2x^2)+4x^2√(1+2x^2)-4x^2√(1+2x^2)]/(1+2x^2)^2
=2√(1+2x^2)/(1+2x^2)
=2×(1+2x^2)^1/2/(1+2x^2)^2
=2/(1+2x^2)^(3/2)
为了表述方便,不妨令√(1+2x²)=t,
2x²=t²-1,于是有:
左边=[2t-2(t²-1)/t]/t²
=2[t²-t²+1]/t³
=2/t³
=2/√(1+2x²)³