Question

1) Calculati:
a) (3 pe langa 1/2 - 1/2) + (1 pe langa 1/3 - 1/3) =
b) 3/14*(7/8*8/3+3 pe langa 1/3*2 pe langa 1/10)
c) 3 : (2 pe langa 3/4 - 1 pe langa 15/28) + 2/3 : 3/2

2) Calculati A + B stiind ca:
A = 7/4*3 + 8/5*3 + ... + 20/17*3 si B= 1/3*4 + 2/3*5 + 3/3*6 + ... + 14/3*17

3) Daca a/b = 6/7 calculeaza:
a) b-a/b+a
b) 3a-2b/a+b

Va multumesc!

Answer 1

$3. \frac{a}{b}= \frac{6}{7}=\ \textgreater \ 7a=6b=\ \textgreater \ a= \frac{6b}{7} \\ a) \frac{b-a}{b+a}= \frac{7/b- \frac{6b}{7} }{7/b+ \frac{6b}{7} }= \frac{ \frac{7b-6b}{7} }{ \frac{7b+6b}{7} }= \frac{1b}{13b}= \frac{1}{13} \\ b) \frac{3a-2b}{a+b}= \frac{3\cdot \frac{6b}{7}-2b }{ \frac{6b}{7}+7/b }= \frac{ \frac{18b}{7}-7/2b }{ \frac{6b+7b}{7} }= \frac{ \frac{18b-14b}{7} }{ \frac{13b}{7} }= \frac{ \frac{4b}{7} }{ \frac{13b}{7} }= \frac{4b}{13b}=\frac{4}{13}$