Question

Tìm x, y, z biết:

a) 4x = 3y; 7y = 5z và 2x + 3y - z = 186

b) 3^x+y + 243 = 3^x+3 + 3^y+2

Answer 1

a) \(4x=3y<=>\frac{x}{3}=\frac{y}{4}=>\frac{x}{15}=\frac{y}{20}\)

\(7y=5z<=>\frac{y}{5}=\frac{z}{7}=>\frac{y}{20}=\frac{z}{28}\)

Ap dung tinh chat bac cau ta duoc:

\(\frac{x}{15}=\frac{y}{20}=\frac{z}{28}=>\frac{2x}{30}=\frac{3y}{60}=\frac{z}{28}=\frac{2x+3y-z}{30+60-28}=\frac{186}{62}=3\)

=> x = 45  ;  y=60  ;  z=84