Question

.............................

Answer 1

Răspuns:

Explicație pas cu pas:

5(5a + 2b) = 4(7a + 2b)

25a + 10b = 28a + 8b

28a - 25a = 10b - 8b

3a = 2b

a = 2b/3

2a - b = 4b/3 - 3b/3 = b/3

a + b = 2b/3 + 3b/3 = 5b/3

(2a - b)/(a + b) = b/3 : 5b/3 = b/3*3/5b = 3b/15b = 1/5

Answer 2

$\it \dfrac{5a+2b}{7a+2b}=\dfrac{4}{5} \Rightarrow \dfrac{5a+2b}{7a+2b-5a-2b}=\dfrac{4}{5-4} \Rightarrow \dfrac{5a+2b}{2a}=4 \Rightarrow \\ \\ \\ \Rightarrow 5a+2b=8a|_{-5a} \Rightarrow 2b=3a|_{:2} \Rightarrow b=1,5a\ \ \ \ \ \ (*)\\ \\ \\ \dfrac{2a-b}{a+b}\ \stackrel{(*)}{=}\ \dfrac{2a-1,5a}{a+1,5a}=\dfrac{0,5a}{2,5a}= \dfrac{^{2)}0,5}{\ 2,5}=\dfrac{1}{5}$