计算 3(2x-7y)(7y+2x)+(4x+5y)(-5y-4x)

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计算 3(2x-7y)(7y+2x)+(4x+5y)(-5y-4x)

计算 3(2x-7y)(7y+2x)+(4x+5y)(-5y-4x)
计算 3(2x-7y)(7y+2x)+(4x+5y)(-5y-4x)

计算 3(2x-7y)(7y+2x)+(4x+5y)(-5y-4x)
3(2x-7y)(2x+7y)+(4x+5y)(-5y-4x)
=3((2x)^2-(7y)^2)-(4x+5y)^2
=3(4x^2-49y^2)-(16x^2+25y^2+40xy)
=-4x^2-172y^2-40xy

3(2x-7y)(7y+2x)+(4x+5y)(-5y-4x)
=3(2x-7y)(2x+7y)-(4x+5y)²
=3(4x²-49y²)+(16x²+40xy+25y²)
=12x²-147y²+16x²+40xy+25y²
=28x²+40xy-122y²