![](data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 72 71" width="72"></svg>)
5x＋3x＋6×1.5=
8x+9
3x-1.5x + 0.3x = 12.6
3x-1.5x + 0.3x = 12.6
1.8x=12.6
x=7
（5x^2-2yx-7y^2)-2(3x^2-xy+3y^2)=?
Urgent···········
=5x^2-2yx-7y^2-6x^2+2xy-6y^2
=-x^2-13y^2
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