Question

a)\(^{5^{x+4_{ }}-3.5^{x+3}}\)=\(^{2.5^9}\)

b)\(\frac{8}{9}\)- \(\frac{1}{72}\)- \(\frac{1}{56}\)- \(\frac{1}{30}\)- \(\frac{1}{20}\)- \(\frac{1}{12}\)- \(\frac{1}{6}\)- \(\frac{1}{3}\)

c)Tìm x,y,z biết:

+) \(\frac{x-2}{x-1}\)= \(\frac{x+4}{x+7}\)                            +)4x = 3y ; 7y = 5z và 2x - 3y +z = 6

+)x : y : z=12 : 9 :5 và xyz = 20                     +)\(\frac{10}{x-5}\)= \(\frac{6}{y-9}\)= \(\frac{14}{z-21}\) và xyz = 6720

+)\(\frac{x}{10}\)=\(\frac{y}{6}\)= \(\frac{z}{21}\) và 5x + y - 2z =28       +)\(\frac{x+16}{9}\)= \(\frac{y-25}{16}\)= \(\frac{z+9}{25}\)và 2x³-1=15