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Question Number 84515 by M±th+et£s last updated on 13/Mar/20

Q.solve  x^3 −x=x!

Q.solvex3x=x!

Answered by mr W last updated on 13/Mar/20

(x+1)x(x−1)=x(x−1)(x−2)!  x≠0, x≠1  ⇒x+1=(x−2)!  let t=x−2  ⇒t+3=t!  ⇒t=3  ⇒x=3+2=5

(x+1)x(x1)=x(x1)(x2)!x0,x1x+1=(x2)!lett=x2t+3=t!t=3x=3+2=5

Commented by mr W last updated on 14/Mar/20

at t=2:  t+3=5, t!=2 ⇒t+3>t!  at t=4:  t+3=7, t!=24 ⇒t+3<t!  that means between t=2 and t=4 there  is a point for t+3=t!. we can check  with t=3: t+3=6=t!=6. i.e. t=3 is  a solution and the only solution,  because upon t=4, t! ≫t+3.

att=2:t+3=5,t!=2t+3>t!att=4:t+3=7,t!=24t+3<t!thatmeansbetweent=2andt=4thereisapointfort+3=t!.wecancheckwitht=3:t+3=6=t!=6.i.e.t=3isasolutionandtheonlysolution,becauseupont=4,t!t+3.

Commented by M±th+et£s last updated on 14/Mar/20

thank you sir   but how did you get that  t+3=t!  t=3    ??

thankyousirbuthowdidyougetthatt+3=t!t=3??

Commented by M±th+et£s last updated on 14/Mar/20

god bless you sir

godblessyousir

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