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-4X2+5X+1=0
(-4X2+5X+1)×(-1/4)=0×(-1/4)(等号左右都乘以 (-1/4),二次项係数化为1)
X2-5/4X-1/4=0
X2-5/4X=1/4 (将常数项移到等号右边)
X2-5/4X+(-5/8)2=1/4+(-5/8)2 (等号两边都加 (-5/8)2)
(X-5/8)2=16/64+25/64 (配成完全平方式)
(X-5/8)2=41/64
X-5/8=± √41/64
X -5/8=√41/8
X=5/8±√41/8
X=5 ± √41/8
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