1) Cho \(\frac{7x+5y}{3x-7y}\)=\(\frac{7z+5t}{3z-7t}\) Chứng minh \(\frac{x}{y}\)=\(\frac{z}{t}\)
2) Tìm x
51x+26y=2000
|x+1.1|+|x+1.2|+|x+1.3|+|x+1.4|=5x
3)Tính
\(\left(\frac{3}{4}-81\right)\)\(\left(\frac{3^2}{5}-81\right)\)\(\left(\frac{3^3}{6}-81\right)\)......\(\left(\frac{3^{2000}}{2003}-81\right)\)