已知x+y=8,xy=12,求x²y+xy²的值解方程①(x+7)(x+5)-(x+1)(x+5)=42②(3x-5)²-(3x+7)²=0
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![已知x+y=8,xy=12,求x²y+xy²的值解方程①(x+7)(x+5)-(x+1)(x+5)=42②(3x-5)²-(3x+7)²=0](/uploads/image/z/1343978-26-8.jpg?t=%E5%B7%B2%E7%9F%A5x%2By%3D8%2Cxy%3D12%2C%E6%B1%82x%26%23178%3By%2Bxy%26%23178%3B%E7%9A%84%E5%80%BC%E8%A7%A3%E6%96%B9%E7%A8%8B%E2%91%A0%28x%2B7%29%28x%2B5%29-%28x%2B1%29%28x%2B5%29%3D42%E2%91%A1%283x-5%29%26%23178%3B-%283x%2B7%29%26%23178%3B%3D0)
已知x+y=8,xy=12,求x²y+xy²的值解方程①(x+7)(x+5)-(x+1)(x+5)=42②(3x-5)²-(3x+7)²=0
已知x+y=8,xy=12,求x²y+xy²的值
解方程①(x+7)(x+5)-(x+1)(x+5)=42
②(3x-5)²-(3x+7)²=0
已知x+y=8,xy=12,求x²y+xy²的值解方程①(x+7)(x+5)-(x+1)(x+5)=42②(3x-5)²-(3x+7)²=0
x²y+xy²
=xy(x+y)
=12x8
96
①(x+7)(x+5)-(x+1)(x+5)=42
x²+12x+35-x²-6x-5=42
6x+30=42
6x=12
x=2
②(3x-5)²-(3x+7)²=0
(3x-5+3x+7)(3x-5-3x-7)=0
-12(6x+2)=0
3x+1=0
x=-1/3
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已知x+y=8,xy=12,求x²y+xy²的值
x²y+xy²=xy(x+y)=12×8=96
解方程①(x+7)(x+5)-(x+1)(x+5)=42
x²+12x+35-x²-6x-5-42=0
6x-12=0
x=2
②(3x-5)²-(3x+7)²=0
(3x-5+3x+7)(3x-5-3x-7)=0
-12(6x+2)=0
3x+1=0
x= -1/3
x^2y+xy^2=xy(x+y)=12*8=96
提取(x+5)(x+7-x-1)=42 (x+5)6=42 x=2
(3x-5+3x+7)(3x-5-3x-7)=0 -12*(6x+2)=0 x=-1/3