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Question Number 67031 by hmamarques1994@gmai.com last updated on 21/Aug/19

    lim_(x→−1) ((((x^5 )^(1/7) +1)/(1+(x^7 )^(1/(9 )) )))^(1/3) =?

limx1x57+11+x793=?

Commented by Tony Lin last updated on 22/Aug/19

(lim_(x→−1) (((5/7)x^((−2)/7) )/((7/9)x^((−2)/9) )))^(1/3)   =(lim_(x→−1) ((45_9 (√x^2 ))/(49_7 (√x^2 ))))^(1/3)   =(((45)/(49)))^(1/3)   please check

(limx157x2779x29)13=(limx1459x2497x2)13=(4549)13pleasecheck

Commented by hmamarques1994@gmail.com last updated on 22/Aug/19

 yes!_     =(((315))^(1/3) /7)≈0,972013   thankyu!

yes!=315370,972013thankyu!

Commented by mathmax by abdo last updated on 22/Aug/19

you have used lim_(x→x_0 )    (((f(x))/(g(x))))^(r ) =(lim_(x→x_0 )  ((f^′ (x))/(g^′ (x))))^r   is this correct?  (its not hospital theorem....)

youhaveusedlimxx0(f(x)g(x))r=(limxx0f(x)g(x))risthiscorrect?(itsnothospitaltheorem....)

Commented by Tony Lin last updated on 22/Aug/19

L′Hospital rule:  if lim_(x→x_0 ) f(x)=lim_(x→x_0 ) g(x)=0 and lim_(x→x_0 ) ((f′(x))/(g′(x))) exists  ⇒lim_(x→x_0 ) ((f(x))/(g(x)))=lim_(x→x_0 ) ((f′(x))/(g′(x)))  if lim_(x→x_0 ) f(x)=±∞, lim_(x→x_0 ) g(x)=±∞ and lim_(x→x_0 ) ((f′(x))/(g′(x))) exists  ⇒lim_(x→x_0 ) ((f(x))/(g(x)))=lim_(x→x_0 ) ((f′(x))/(g′(x)))  if lim_(x→x_0 ) f(x) exists  lim_(x→x_0 ) [f(x)]^n =[lim_(x→x_0 ) f(x)]^n   ⇒Power Law of Limit  or we can use Composition Law to know  if f is continuous at lim_(x→x_0 ) g(x)  then lim_(x→x_0 ) f(g(x))=f(lim_(x→x_0 ) g(x))

LHospitalrule:iflimxx0f(x)=limxx0g(x)=0andlimxx0f(x)g(x)existslimxx0f(x)g(x)=limxx0f(x)g(x)iflimxx0f(x)=±,limxx0g(x)=±andlimxx0f(x)g(x)existslimxx0f(x)g(x)=limxx0f(x)g(x)iflimxx0f(x)existslimxx0[f(x)]n=[limxx0f(x)]nPowerLawofLimitorwecanuseCompositionLawtoknowiffiscontinuousatlimxx0g(x)thenlimxx0f(g(x))=f(limxx0g(x))

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