已知x-2y=15,xy=-25,求x的2次方加4y的2次方减1的值

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已知x-2y=15,xy=-25,求x的2次方加4y的2次方减1的值已知x-2y=15,xy=-25,求x的2次方加4y的2次方减1的值已知x-2y=15,xy=-25,求x的2次方加4y的2次方减1

已知x-2y=15,xy=-25,求x的2次方加4y的2次方减1的值
已知x-2y=15,xy=-25,求x的2次方加4y的2次方减1的值

已知x-2y=15,xy=-25,求x的2次方加4y的2次方减1的值
x的2次方加4y的2次方减1
=X^2-4XY+4Y^2-1+4XY
=(X-2Y)^2-1+4XY
=15^2-1-100
=124

324

(x-2y)^2=x^2-4*x*y+4y^2=x^2+100+4y^2=15^2=225。所以x^2+4y^2-1=124

(x-2y)^2
=x^2+4y^2-4xy
=x^2+4y^2+100
=15*15=225
x^2+4y^2=125
x^2+4y^2-1
=125-1=124

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