數學極難問題

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1.)18(3+2x)^2 - 50 (2x - 3)^2
=18(3+2x)(3+2x)-50(2x-3)(2x-3)
=18(9+6x+6x+4x^2)-50(4x^2-6x-6x+9)
=18(9+12x+4x^2)-50(4x^2-12x+9)
=162+216x+72x^2-200x^2+600x-450
= -288+816x-128x^2

2.) 72 - 50 (2x + 3y)^2
=72-50(2x + 3y)(2x + 3y)
=72-50(4x^2+6xy+6xy+9y^2)
=72-50(4x^2+12xy+9y^2)
= 72-200x^2-600xy-450y^2

3.) 25(x+5y)^2 - 9 (3x - 2y) ^2
=25(x+5y)(x+5y)-9(3x - 2y)(3x - 2y)
=25(x^2+10xy+25y^2)-9(9x^2-12xy+4y^2)
=25x^2+250xy+625y^2-81x^2+108xy-36y^2
=25x^2-81x^2+250xy+108xy+625y^2-36y^2
= -56x^2+358xy+589y^2

1.18(9+4x)-50(4x-9)
=162+72x-200x+450
=612-128x

2.72-50(4x+9y)
=72-200x-450y

3.25(x．x+25y)-9(9x-4y)
=25x^2+625y-81x+36y
=25^2+661y-81x

唔知岩唔岩架...
你自己睇下啦~
i hope this can help you!!

1. 18(3+2x)^2 - 50 (2x - 3)^2
=18(9+12x+4x^2)- 50 (4x^2-12x+9)
=162+216x+72x^2-200x^2+600x-450
=-288+16x-128x^2