Toán Tìm nghiệm dương `x^5 +x^4 – 3x^3 – x^2 -x – 1=0` 09/07/2021 By Everleigh Tìm nghiệm dương `x^5 +x^4 – 3x^3 – x^2 -x – 1=0`
`x^5+x^4-3x^3-x^2-x-1=0` `⇔ x^5-x^4+2x^4-x^3-2x^3-2x^2+x^2-x-1=0` `⇔ x^3.(x^2-x-1).2x^2.(x^2-x-1)+x^2-x-1=0` `⇔ (x^2-x-1).(x^3+2x^2+1)=0` `⇔ TH1: x=(1+√5)/2` `⇔ TH2: x=(1-√5)/2` Vậy……………………. Trả lời
`x^5+x^4-3x^3-x^2-x-1=0` `⇔ x^5-x^4+2x^4-x^3-2x^3-2x^2+x^2-x-1=0` `⇔ x^3.(x^2-x-1).2x^2.(x^2-x-1)+x^2-x-1=0` `⇔ (x^2-x-1).(x^3+2x^2+1)=0` `⇔ TH1: x=(1+√5)/2` `⇔ TH2: x=(1-√5)/2` Vậy `x=(1+√5)/2` hoặc `x=(1-√5)/2` Trả lời
`x^5+x^4-3x^3-x^2-x-1=0`
`⇔ x^5-x^4+2x^4-x^3-2x^3-2x^2+x^2-x-1=0`
`⇔ x^3.(x^2-x-1).2x^2.(x^2-x-1)+x^2-x-1=0`
`⇔ (x^2-x-1).(x^3+2x^2+1)=0`
`⇔ TH1: x=(1+√5)/2`
`⇔ TH2: x=(1-√5)/2`
Vậy…………………….
`x^5+x^4-3x^3-x^2-x-1=0`
`⇔ x^5-x^4+2x^4-x^3-2x^3-2x^2+x^2-x-1=0`
`⇔ x^3.(x^2-x-1).2x^2.(x^2-x-1)+x^2-x-1=0`
`⇔ (x^2-x-1).(x^3+2x^2+1)=0`
`⇔ TH1: x=(1+√5)/2`
`⇔ TH2: x=(1-√5)/2`
Vậy `x=(1+√5)/2` hoặc `x=(1-√5)/2`