(2/X方+6X+5)+(5/X方+6X+8)=(8/X方+6X+9)
人气:320 ℃ 时间:2020-06-12 14:07:36
解答
(2/X方+6X+5)+(5/X方+6X+8)=(8/X方+6X+9)
令t=x^2+6x+8
2/(t-3)+5/t=8/(t+1)
2t(t+1)+5(t-3)(t+1)=8t(t-3)
2t^2+2t+5t^2+5t-15t-15=8t^2-24t
t^2-16t+15=0
(t-15)(t-1)=0
t=15或t=1
当t=15时
x^2+6x+8=15
x^2+6x-7=0
(x-1)(x+7)=0
x=1 或x=-7
当t=1时
x^2+6x+8=1
x^2+6x+7=0
用公式法解得
x=(-6+√6^2-4*1*7)/2*1=-3+√2
或x=(-6-√6^2-4*1*7)/2*1=-3-√2
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