\(1990\times1990-1992\times1998\)
\(=1990\times1990-\left(1992-2\right)\times\left(1998+2\right)\)
\(=1990\times1990-1990\times1990\)
\(=0\)
\(1990\times1990-1992\times1998\)
\(=1990\times1990-\left(1992-2\right)\times\left(1998+2\right)\)
\(=1990\times1990-1990\times2000\)
\(=3960100-3980000\)
\(=-1990.\)
1990×1990−1992×1998
=1990×1990−(1992−2)×(1998+2)
=1990×1990−1990×\(2000\)
\(=1990\times(1990-2000)\)
\(=1990\times(-10)\)
\(=-19900\)