Đặt \(\frac{x}{2015}=\frac{y}{2016}=\frac{z}{2017}=k\)

\(\Rightarrow x=2015k;y=2016k;z=2017k\)

Ta có:

\(\left(x-z\right)^3=\left(2015k-2017k\right)^3=-8k^3\left(1\right)\)

Mặt khác:

\(-8\left(x-y\right)^2\left(z-y\right)=-8\left(2015k-2016k\right)^2\left(2017k-2016k\right)\)

\(=-8k^2\cdot k=-8k^3\left(2\right)\)

Từ ( 1 );( 2 ) suy ra đpcm

\(a ) Ta có : a / b = 2 và b / c = 3\)

\(\Rightarrow\)\(a = 2b \)\(và \)\(b = 3c\)

\(A = ( a + b ) / ( b + c ) \)

\(A = ( 2b + b ) / ( 3c + c )\)

\(A = 3b / 4c\)

\(A = 3 / 4 . b / c \)

\(A = 3 / 4 . 3 \)

\(A = 9 / 4\)

\(2^x.8^{x-1}=32\Leftrightarrow2^x=2^x.2^{3\left(x-1\right)}=32\)

\(\Rightarrow2^{x+3\left(x-1\right)}=32=2^5\Leftrightarrow x+3\left(x-1\right)=5\)

\(\Rightarrow x+3x-1.3=5\Leftrightarrow1x+3x=4x=5-3=2\)

\(\Rightarrow x=2\div4=\frac{2}{4}\)                    Vậy \(x=\frac{2}{4}\)

\(x+2x=\frac{7}{8}-\frac{1}{4}\)

\(3x=\frac{5}{8}\)

\(x=\frac{5}{8}\times\frac{1}{3}\)

\(x=\frac{5}{24}\)

x+1/4=7/8 -2x

=>x+2x=7/8 -1/4

=>3x=5/8

=>x=5/8 :3

=> x=5/24

hok tốt 

đề bài là gì vậy bạn?

vì  (x⁵-x)⁴ luôn >hay=0

      (3y-4y)⁶ luôn< hay=0

suy ra: để .................=0 thì (x⁵-x)⁴=0 và (3y-4y)⁸=0

\(Đặt x / 2 = y / 5 = z / 7 = k \)

\(\Rightarrow\)\(x = 2k ; y = 5k ; z = 7k\)

\(A = ( 4x - y + z ) / ( x + 2y - z )\)

\(A = ( 4 . 2k - 5k + 7k ) / ( 2k + 2 . 5k - 7k ) \)

\(A = ( 8k - 5k + 7k ) / ( 2k + 10k - 7k )\)

\(A = 10 k / 5k\)

\(A = 2\)