Question

Сократив дробь 4m²+3mn-n²/3m²+4mn+n² вычислите ее значение если m/n=5/12

Answer 1

$\frac{4m^2+3mn-n^2}{3m^2+4mn+n^2}=\frac{\frac{4m^2}{n^2}+\frac{3mn}{n^2}-\frac{n^2}{n^2}}{\frac{3m^2}{n^2}+\frac{4mn}{n^2}+\frac{n^2}{n^2}}=\frac{4(\frac{m}{n})^2+3(\frac{m}{n})-1}{3(\frac{m}{n})^2+4(\frac{m}{n})+1}=\\=\frac{4(\frac{5}{12})^2+3(\frac{5}{12})-1}{3(\frac{5}{12})^2+4(\frac{5}{12})+1}=\frac{4\cdot25+3\cdot5\cdot12-12^2}{3\cdot25+4\cdot5\cdot12+12^2}=\frac{136}{459}=\frac{8}{27}.$

Ответ: $\frac{8}{27}.$