Question

Просто не понимаю....

Answer 1

$1)frac{14b^{2} }{5}-frac{9b^{2} }{5}=frac{14b^{2}-9b^{2}}{5}=frac{5b^{2} }{5}=b^{2} \\2)frac{12b}{7}-frac{3b}{7}=frac{12b-3b}{7}=frac{9b}{7}\\ 3)frac{1}{a+b}-frac{1}{a-b}=frac{a-b-a-b}{(a-b)(a+b)}=-frac{2b}{a^{2}-b^{2}}\\4)frac{2}{3a}+frac{b}{c}=frac{2c+3ab}{3ac}$

$5)frac{2a-4}{4a} +frac{3a+4}{4a}=frac{2a-4+3a+4}{4a}=frac{5a}{4a}=frac{5}{4}=1,25\\6)frac{3}{ab}-frac{b}{2ac} =frac{6c-b^{2} }{2abc}\\7)frac{1}{a^{2}b^{2}}-frac{1}{ab}=frac{1-ab}{a^{2}b^{2}}\\8)frac{5}{x-5}-frac{x}{x-5}=frac{5-x}{x-5}=-frac{x-5}{x-5}=-1$