(x+y)的平方-16(x-y)的平方=初二下册数学课本61页复习题

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(x+y)的平方-16(x-y)的平方=初二下册数学课本61页复习题

(x+y)的平方-16(x-y)的平方=初二下册数学课本61页复习题
(x+y)的平方-16(x-y)的平方=
初二下册数学课本61页复习题

(x+y)的平方-16(x-y)的平方=初二下册数学课本61页复习题
(X+Y)²-16(X-Y)²
=〔X+Y+4(X-Y)〕〔X+Y-4(X-Y)〕
=(X+Y+4X-4Y)(X+Y-4X+4Y)
=(5X-3Y)(5Y-3X)

(x+y)^2-16(x-y)^2
=(x+y)^2 - [ 4(x-y) ]^2
=[ (x+y) + 4(x-y) ]·[ (x+y) - 4(x-y) ]
=(x+y+4x-4y)·(x+y-4x+4y)
=(5x-3y)·(-3x+5y)
=-15x^2+25xy+9xy-15y^2
=-15x^2+34xy-15y^2