0.4X^2+5X-5=0

问题描述:

0.4X^2+5X-5=0

0.4X^2+5X-5=0
(2/5)X^2+5X-5=0
X^2+(25/2)X-25/2=0
(X+25/4)^2-625/16-25/2=0
(X+25/4)^2=825/16
(X+25/4)=5根号33/4
或(X+25/4)=-5根号33/4
X1=(5根号33-25)/4
X2=-(5根号33+25)/4

等价于 4X^2+50X-50=0
x=(-25+-5*根号33)/4
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