(X+5y)(x+4y)-(x-5y)(x+5y),其中x=3,y=-1/3化简求值

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(X+5y)(x+4y)-(x-5y)(x+5y),其中x=3,y=-1/3化简求值
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(X+5y)(x+4y)-(x-5y)(x+5y),其中x=3,y=-1/3化简求值
(X+5y)(x+4y)-(x-5y)(x+5y),其中x=3,y=-1/3化简求值

(X+5y)(x+4y)-(x-5y)(x+5y),其中x=3,y=-1/3化简求值
原式=x^2+9xy+20y^2-(x^2-25y^2)
=9xy+45y^2
把x=3,y=-1/3
原式=-9+45*1/9=-4