a=2002^2+2002^2×2003^2＋2003^2
=2002^2+2002^2×(2002+1)^2＋(2002+1)^2
=2002^2+2002^2×(2002^2+2×2002+1)+2002^2+2×2002+1
=2002^2+2002^4+2×2002^3+2002^2+2002^2+2×2002+1
=2002^4+2×2002^3+3×2002^2+2×2002+1
=2002^4+2×2002^3+2002^2+2×2002^2+2×2002+1
=(2002^2+2002)^2+2×(2002^2+2002)+1
=(2002^2+2002+1)^2
=【2002（2002+1）+1】^2
=(2002x2003+1)²
得证
如果本题有什么不明白可以追问,