数学题(用十字相乘法)4n^2+4n-156a^2+a-355x^2-8x-134x^2+15x+915x^2+x-26y^2+19y+1020-9y-20y^27(x-1)^2+4(x-1)(x+2)-20(y+2)^2

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数学题(用十字相乘法)4n^2+4n-156a^2+a-355x^2-8x-134x^2+15x+915x^2+x-26y^2+19y+1020-9y-20y^27(x-1)^2+4(x-1)(x+2)-20(y+2)^2

数学题(用十字相乘法)4n^2+4n-156a^2+a-355x^2-8x-134x^2+15x+915x^2+x-26y^2+19y+1020-9y-20y^27(x-1)^2+4(x-1)(x+2)-20(y+2)^2
数学题(用十字相乘法)
4n^2+4n-15
6a^2+a-35
5x^2-8x-13
4x^2+15x+9
15x^2+x-2
6y^2+19y+10
20-9y-20y^2
7(x-1)^2+4(x-1)(x+2)-20(y+2)^2

数学题(用十字相乘法)4n^2+4n-156a^2+a-355x^2-8x-134x^2+15x+915x^2+x-26y^2+19y+1020-9y-20y^27(x-1)^2+4(x-1)(x+2)-20(y+2)^2
答:
1.原式=(2n-3)(2n+5)
2.原式=(3a-7)(2a+5)
3.原式=(5x-13)(x+1)
4.原式=(4x+3)(x+3)
5.原式=(3x-1)(5x+2)
6.原式=(2y+5)(3y+2)
7.原式=-(4y+5)(5y-4)
8.原式=[7(x-1)-10(y+2)][(x-1)+2(y+2)]=(7x-10y-27)(x+2y+3)