解方程组{x/2+y/3=2,2(x+y+1)=3(1-y)-15;

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解方程组{x/2+y/3=2,2(x+y+1)=3(1-y)-15;
解方程组{x/2+y/3=2,2(x+y+1)=3(1-y)-15;

解方程组{x/2+y/3=2,2(x+y+1)=3(1-y)-15;
x/2+y/3=2
两边乘6
3x+2y=12 (1)
2(x+y+1)=3(1-y)-15;
2x+2y+2=3-3y-15
2x+5y=-14 (2)
(1)×5-(2)×2
15x-4x=60+28
11x=88
x=8
y=(-14-2x)/5=-6

x=5y/4
x^2=25y^2/16
所以原式=(25y^2/16-y^2)/y^2
=(9y^2/16)/y^2
=9/16
原式=(a2-b2-a2+2ab-b2+2ab-2b2)÷4(a-b)
=(-4b2+4ab)÷4(a-b)
=4b(a-b)÷a(a-b)
=b