用适当的方法解 x²-8x=20(2) 2x²-6x-1=0(3)根号2x²-4x=4根号2(4)(x-2)²-4(x-2)=-4
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![用适当的方法解 x²-8x=20(2) 2x²-6x-1=0(3)根号2x²-4x=4根号2(4)(x-2)²-4(x-2)=-4](/uploads/image/z/1638251-35-1.jpg?t=%E7%94%A8%E9%80%82%E5%BD%93%E7%9A%84%E6%96%B9%E6%B3%95%E8%A7%A3+x%26%23178%3B-8x%3D20%EF%BC%882%EF%BC%89+2x%26%23178%3B-6x-1%3D0%EF%BC%883%EF%BC%89%E6%A0%B9%E5%8F%B72x%26%23178%3B-4x%3D4%E6%A0%B9%E5%8F%B72%EF%BC%884%EF%BC%89%EF%BC%88x-2%29%26%23178%3B-4%28x-2%29%3D-4)
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用适当的方法解 x²-8x=20(2) 2x²-6x-1=0(3)根号2x²-4x=4根号2(4)(x-2)²-4(x-2)=-4
用适当的方法解 x²-8x=20
(2) 2x²-6x-1=0
(3)根号2x²-4x=4根号2
(4)(x-2)²-4(x-2)=-4
用适当的方法解 x²-8x=20(2) 2x²-6x-1=0(3)根号2x²-4x=4根号2(4)(x-2)²-4(x-2)=-4
(1)x²-8x=20
x²-8x-20=0
(x-10)(x+2)=0
x=10或x=-2
(2)2x²-6x-1=0
x²-3x=1/2
x²-3x+(3/2)²=1+(3/2)²
(x-3/2)²=13/4
x-3/2=±(√13)/2
x=(3+√13)/2或x=(3-√13)/2
(3)根号2x²-4x=4根号2
x²-2√2x=4
x²-2√2x+(√2)²=4+(√2)²
(x-√2)²=6
x-√2=±√6
x=√2+√6或x=√2-√6
(4)(x-2)²-4(x-2)=-4
(x-2)²-4(x-2)+4=0
(x-2-2)²=0
(x-4)²=0
x=4