Question

运用乘法公式计算

运用乘法公式计算①﹙5mn-2x²﹚﹙5mn+2x²﹚②2m²＋2﹙x＋m﹚﹙x-m﹚③﹙x＋3﹚²－﹙x＋3﹙x-3﹚④﹙x-2y+4﹙x＋2y-4﹚

Answer 1

①﹙5mn-2x²﹚﹙5mn+2x²﹚
=（5mn）²-4x²
=25m²n²-4x²
②2m²＋2﹙x＋m﹚﹙x-m﹚
=2m²＋2﹙x²-m²﹚
=2x²
③﹙x＋3﹚²－﹙x＋3)﹙x-3﹚
=﹙x＋3﹚²－﹙x²-3²﹚
=x²+6x+9-x²+9
=6x+18
④﹙x-2y+4)﹙x＋2y-4﹚

=[x-(2y-4)][x＋(2y-4﹚]
=x²-(2y-4)²
=x²-4y²+16y-16

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Answer 2

运用乘法公式计算
①﹙5mn-2x²﹚﹙5mn+2x²﹚
=25m^2n^2-4x^4
②2m²＋2﹙x＋m﹚﹙x-m﹚
=2m^2+2(x^2-m^2)
=2x^2
③﹙x＋3﹚²－﹙x＋3﹙x-3﹚
=(x+3)^2-(x^2-9)
=x^2+9+6x-x^2-9
=6x
④﹙x-2y+4)﹙x＋2y-4﹚
=x^2-(2y-4)^2
=x^2-4y^2+16y-16

Answer 3

1.25m*2n*2-4x*4
2.2x*2
3.x*2+8x
4.x*2+4y*2+16x-16