202*198用平方差公式计算
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202*198用平方差公式计算
202×198
=(200+2)×(200-2)
=200²-2²
=40000-4
=39996
再问: 81/4*(-79/4)
再答: 81/4*(-79/4) =-81/4*79/4 =-(80+1)(80-1)/16 =-(80²-1²)/16 =-(6400-1)/16 =-6399/16
=(200+2)×(200-2)
=200²-2²
=40000-4
=39996
再问: 81/4*(-79/4)
再答: 81/4*(-79/4) =-81/4*79/4 =-(80+1)(80-1)/16 =-(80²-1²)/16 =-(6400-1)/16 =-6399/16