20. Представьте в виде дроби выражение: 1) 6m/(2b) + 7m/(2b); 2) 14a/(9b) − 5a/(9b); 3) (4b − 15c)/(18a) + (2b + 3c)/(18a); 4) (8m − 5n)/(mn) − (2m − 5n)/(mn); 5) 2y/(y² − 49) − 14/(y² − 49); 6) (x² + 12x)/(25 − x²) − (2x − 25)/(25 − x²).

Question

Вопрос:

Accepted Answer

\(\dfrac{6m+7m}{2b}=\dfrac{13m}{2b}\).
\(\dfrac{14a-5a}{9b}=\dfrac{9a}{9b}=\dfrac{a}{b}\).
\(\dfrac{4b-15c+2b+3c}{18a}=\dfrac{6b-12c}{18a}=\dfrac{b-2c}{3a}\).
\(\dfrac{8m-5n-2m+5n}{mn}=\dfrac{6m}{mn}=\dfrac{6}{n}\).
\(\dfrac{2y-14}{y^2-49}=\dfrac{2(y-7)}{(y-7)(y+7)}=\dfrac{2}{y+7}\).
\(\dfrac{x^2+12x-2x+25}{25-x^2}=\dfrac{x^2+10x+25}{25-x^2}=\dfrac{(x+5)^2}{(5-x)(5+x)}=\dfrac{x+5}{5-x}\).

В пункте 5: \(y\ne\pm7\). В пункте 6: \(x\ne\pm5\).

Ответ: 1) \(\dfrac{13m}{2b}\); 2) \(\dfrac{a}{b}\); 3) \(\dfrac{b-2c}{3a}\); 4) \(\dfrac{6}{n}\); 5) \(\dfrac{2}{y+7}\); 6) \(\dfrac{x+5}{5-x}\).