Toán Lớp 8: timf x thoa man (5x-9)^3+(11-5x)^3=386 giúp vs bài này dễ lắm

Question

Toán Lớp 8:  timf x thoa man (5x-9)^3+(11-5x)^3=386 giúp vs bài này dễ lắm

maitrucloan · Answer

(5x-9)&sup3;+(11-5x)&sup3;=386       (5x-9+11-5x)[(5x-9)&sup2;-(5x-9)(11-5x)+(11-5x)&sup2;]=386       2[(5x-9)&sup2;-5x(11-5x)-9(11-5x)+(11-5x)&sup2;]=386       (5x-9)&sup2;-5x(11-5x)-9(11-5x)+(11-5x)&sup2;=193       25x&sup2;-90x+81-55x+25x&sup2;-99+45x+121-110x+25x&sup2;=193       (25x&sup2;+25x&sup2;+25x&sup2;)-(90x+55x-45x+110x)+(81-99+121)=193       75x&sup2;-210x+103=193       75x&sup2;-210x=90       75x.(x-2,8)=90       Mk chỉ l&agrave;m đc đến đ&acirc;y th&ocirc;i nha       Cho mk xin hay nhất please       Thank you       #Muoi

quynhthanhnghi · Answer

Giải đáp:     &darr;&darr;     Lời giải và giải thích chi tiết:     (5x-9)^3+(11-5x)^3=386   (5x-9+11-5x)[(5x-9)^2-(5x-9)(11-5x)+(11-5x)^2]=386   2[(5x-9)^2-5x(11-5x)-9(11-5x)+(11-5x)^2]=386   (5x-9)^2-5x(11-5x)-9(11-5x)+(11-5x)^2=193   25x^2-90x+81-55x+25x^2-99+45x+121-110x+25x^2=193   (25x^2+25x^2+25x^2)-(90x+55x-45x+110x)+(81-99+121)=193   75x^2-210x+103=193   75x^2-210x=90   75x.(x-2,8)=90.