用适当的方法解 x²-8x=20 急(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 急(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/2547712-64-2.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+%E6%80%A5%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)
用适当的方法解 x²-8x=20 急(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 急
(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 急(2) 2x²-6x-1=0(3)根号2x²-4x=4根号2(4)(x-2)²-4(x-2)=-4
x²-8x=20
x²-8x+16=36
(x-4)²=6²
x-4=6,或者,x-4=-6
x=10,或者,x = -2
(2) 2x²-6x-1=0
x²-3x-0.5=0
x²-3x+2.25=2.75
(x-1.5)²=(√11/2)²
x-1.5=√11/2,或者,x-1.5=-√11/2
x=(3+√11)/2,或者,x =(3-√11)/2
(3)根号2x²-4x=4根号2
x²-2√2x=4
x²-2√2x+2=6
(x-√2)²=(√6)²
x-√2=√6,或者,x-√2=-√6
x=√2+√6,或者,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=0
x=4