14(a^2+b^2+c^2)=(a+2b+3c),求证a∶b∶c=1∶2∶3.在△ABC中,AD⊥BC于D,AB=9,AC=6,M是AD上任意一点,则MB^2-MC^2=( ).已知:M、N为等腰直角三角形ABC斜边AB上两点,且∠MCN=45°,求证:AM^2+BN^2=MN^2.要思路
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![14(a^2+b^2+c^2)=(a+2b+3c),求证a∶b∶c=1∶2∶3.在△ABC中,AD⊥BC于D,AB=9,AC=6,M是AD上任意一点,则MB^2-MC^2=( ).已知:M、N为等腰直角三角形ABC斜边AB上两点,且∠MCN=45°,求证:AM^2+BN^2=MN^2.要思路](/uploads/image/z/2581112-56-2.jpg?t=14%28a%5E2%2Bb%5E2%2Bc%5E2%29%3D%28a%2B2b%2B3c%29%2C%E6%B1%82%E8%AF%81a%E2%88%B6b%E2%88%B6c%3D1%E2%88%B62%E2%88%B63.%E5%9C%A8%E2%96%B3ABC%E4%B8%AD%2CAD%E2%8A%A5BC%E4%BA%8ED%2CAB%3D9%2CAC%3D6%2CM%E6%98%AFAD%E4%B8%8A%E4%BB%BB%E6%84%8F%E4%B8%80%E7%82%B9%2C%E5%88%99MB%5E2-MC%5E2%3D%EF%BC%88+%EF%BC%89.%E5%B7%B2%E7%9F%A5%EF%BC%9AM%E3%80%81N%E4%B8%BA%E7%AD%89%E8%85%B0%E7%9B%B4%E8%A7%92%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E6%96%9C%E8%BE%B9AB%E4%B8%8A%E4%B8%A4%E7%82%B9%2C%E4%B8%94%E2%88%A0MCN%EF%BC%9D45%C2%B0%2C%E6%B1%82%E8%AF%81%EF%BC%9AAM%EF%BC%BE2%EF%BC%8BBN%EF%BC%BE2%EF%BC%9DMN%EF%BC%BE2.%E8%A6%81%E6%80%9D%E8%B7%AF)
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