Question

\(\frac{x}{y}=\frac{3}{4}\)và 2x+5y=10

21x=19yvà x-y =4

\(\frac{x}{5}=\frac{y}{3}\)và x²-y²=4(x,y>0)

Answer 1

a) Ta có: \(\frac{x}{y}=\frac{3}{4}\Rightarrow4x=3y\Rightarrow\frac{x}{3}=\frac{y}{4}=\frac{2x+5y}{6+20}=\frac{10}{26}=\frac{5}{13}\)

\(x=\frac{5}{13}.3=\frac{15}{13}\)

\(y=\frac{5}{13}.4=\frac{20}{13}\)

b) Ta có: \(21x=19y\Rightarrow\frac{x}{19}=\frac{y}{21}=\frac{x-y}{19-21}=\frac{4}{-2}=-2\)

x = (-2) x 19 = -38

y = (-2) x 21 = -42

c) Ta có: \(\frac{x}{5}=\frac{y}{3}\Rightarrow\frac{x^2}{5^2}=\frac{y^2}{3^2}=\frac{x^2-y^2}{5^2-3^2}=\frac{4}{16}=\frac{1}{4}\)

\(x^2=\frac{1}{4}.25=\frac{25}{4}\Rightarrow x=+_-\frac{5}{2}\)

\(y^2=\frac{1}{4}.9=\frac{9}{4}\Rightarrow+_-\frac{3}{2}\)

nha bạn!