Question

1) a)
Dacă a/b=2/7, calculati 3a/b .
    b)
Dacă x/y=1/2 si y/z=3/4, calculați x/z si xz/y la puterea doua .

2)
Aflați x din proporția  a) x/4=5/3, b)x/x+1=3/4

Answer 1

1) a)   $\frac{a}{b}=\frac{2}{7} \\ \frac{3a}{b}=3* \frac{a}{b}=3* \frac{2}{7} = \frac{3*2}{7} = \frac{6}{7}$

b)  $\frac{x}{y}= \frac{1}{2} => y=2x \\ \frac{y}{z} =\frac{3}{4} => \frac{2x}{z}=\frac{3}{4} =>2* \frac{x}{z} =\frac{3}{4}=> \frac{x}{z} = \frac{ \frac{3}{4} }{2} => \frac{x}{z} = \frac{3}{8}$

2) a)$\frac{x}{4} = \frac{5}{3} => x =\frac{4*5}{3} => x= \frac{20}{3} => x=6,(6)$
    b)$\frac{x}{x+1} = \frac{3}{4} => 3(x+1)=4x =>3x+3=4x |-3x =>x=3$