已知x-3y=2x+y-15=1,则x^2-4xy+y^2明天确认答案谁对
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已知x-3y=2x+y-15=1,则x^2-4xy+y^2明天确认答案谁对
已知x-3y=2x+y-15=1,则x^2-4xy+y^2
明天确认答案谁对
已知x-3y=2x+y-15=1,则x^2-4xy+y^2明天确认答案谁对
x - 3y =1 x =3y+1 代入2x+y-15=1 得 y=2
则x =7
x^2-4xy+y^2 =49 - 56 + 4 = -3
x-3y=2x+y-15=1
解方程得:x=7、y=2
x^2-4xy+y^2=47-56+4=-5
-3
x-3y=1............1
2x+y-15=1
2x+y=16..............2
2式-1式*2得
7y=14
y=2
x-3y=1
x-3*2=1
x-6=1
x=7
x^2-4xy+y^2
=x^2-2xy+y^2-2xy
=(x-y)^2-2xy
=(7-2)^2-2*2*7
=5^2-28
=25-28
=-3
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