(4x-3y)(5x+2y)-2x(9x-5y) 等于多少

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(4x-3y)(5x+2y)-2x(9x-5y) 等于多少

(4x-3y)(5x+2y)-2x(9x-5y) 等于多少
(4x-3y)(5x+2y)-2x(9x-5y) 等于多少

(4x-3y)(5x+2y)-2x(9x-5y) 等于多少
(4x-3y)(5x+2y)-2x(9x-5y)
=20x^2+8xy-15xy-6y^2-18x^2+10xy
=2x^2+3xy-6y^2

=20x^2+8xy-15xy-6y^2-18x^2+10y^2
=2x^2-7xy+4y^2
上面^是平方的意思

=4x*5x+4x*2y-3y*5x-3y*2y-2x*9x+2x*5y
=20x+8xy-15xy-6y平方-18x平方+10xy
=20x+3xy-6y平方-18x平方

(4x-3y)(5x+2y)-2x(9x-5y)
=20x²+8xy-15xy-6y²-18x²+10xy
=2x²-3xy-6y²

(4x-3y)(5x+2y)-2x(9x-5y)
=20x^2+8xy-15xy-6y^2-18x^2+10xy
=2x^2+3xy-6y^2