Bài 1: Cho dãy tỉ số =nhau 2a+b+c+d / a = a+2b+c+d / b = a+b+2c+d / c = a+b+c+2d /d tính M = a+b/ c+d + b+c/ d+a + c+d/ a+b + d+a/b+c

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1. $\frac{2a+b+c+d}{a}$=$\frac{a+2b+c+d}{b}$=$\frac{a+b+2c+d}{c}$=$\frac{a+b+c+2d}{d}$=$\frac{2a+b+c+d+a+2b+c+d+a+b+2c+d+a+b+c+2d}{a+b+c+d}$=4

   2a+b+c+d=4a

   2a=b+c+d

   Tương tự ta có:2b=a+c+d

   2c=a+b+d

   2d=a+b+c

   =>2a+2b=b+c+d+a+c+d=>a+b+2c+2d

   =>a+b=2c+2d

   =>$\frac{a+b}{c+d}$=2

   Tương tự ta có:$\frac{b+c}{d+a}$=2

   $\frac{c+d}{a+b}$=2 

   $\frac{d+a}{b+c}$=2

   =>M=2+2+2+2=8

   Trả lời