\(\frac{x}{5}\)=\(\frac{y}{2}\)=\(\frac{x-y}{5-2}\)=\(\frac{21}{3}\)=7

Suy ra 

 \(\frac{x}{5}\)=7 => x=7.5=35

\(\frac{y}{2}\)=7 => y=7.2=14

vậy x=35; y=14

Đặt\(\frac{a}{b}=\frac{c}{d}=k\Rightarrow a=bk;c=dk\)

Khi đó: \(\frac{2a+5b}{3a-4b}=\frac{2bk+5b}{3bk-4b}=\frac{b\left(2k+5\right)}{b\left(3k-4\right)}=\frac{2k+5}{3k-4}\)

            \(\frac{2c+5d}{3c-4d}=\frac{2dk+5d}{3dk-4d}=\frac{d\left(2k+5\right)}{d\left(3k-4\right)}=\frac{2k+5}{3k-4}\)

\(\Rightarrow\frac{2a+5b}{3a-4b}=\frac{2c+5d}{3c-4d}\left(=\frac{2k+5}{3k-4}\right)\)

Từ\(\frac{a}{b}\)=\(\frac{c}{d}\)suy ra \(\frac{a}{c}\)=\(\frac{b}{d}\)( t/c TLT)

Áp dụng tính chất của dãy TSBN ta có:\(\frac{a}{c}\)=\(\frac{b}{d}\)=\(\frac{2a+5b}{2c+5d}\)=\(\frac{3a-4b}{3c-4d}\)

Từ \(\frac{2a+5b}{2c+5d}\)=\(\frac{3a-4b}{3c-4d}\) suy ra\(\frac{2a+5b}{3a-4b}\)=\(\frac{2c+5d}{3c-4d}\)(t/c TLT)

(x-2)⁸=(x-2)⁶

Vi (x-2)⁸ va (x-2)⁶ co so mu cung tinh chan le nen:

x-2=0

hoac x-2=1

hoac x-2=-1

=> x=2

hoac x=3

hoac x=1

Trung binh cong cac gia tri cua x la: (2+3+1):3=2

B=(16^10+32^7)

=(2^4)^10+(2^5)^7

=2^40+2^35

=2^35(2^5+1)

=2^35(32+1)

=2^35.33

=> B chia hết cho 33

=> 16^10+32^7 chia hết cho 33