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最佳答案:2x²-4x-7=0x²-2x-7/2=0x²-2x=7/2x²-2x+1=9/2(x-1)²=9/2x-1=±3√2/2x1=1+3√2/2, x2=1-3√
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最佳答案:同时除以a得想x^2+b/ax+c/ax=0 (x+b/2a)^2=b^2/4a^2-c/ax+b/2a=√[b^2/4a^2-c/a]或-√[b^2/4a^2