Question

40 БАЛЛОВ!
АЛГЕБРА 7 КЛАСС ФОРМУЛЫ СОКРАЩЁНОГО УМНОЖЕНИЯ ФОТО 123-129

Answer 1

$\displaystyle 123)..( \frac{a+b}{a}- \frac{2b}{a+b})*(a+b)= \frac{((a+b)^{2}-2ab)(a+b)}{a(a+b)}= \\ \\ = \frac{a^{2}+2ab+b^{2}-2ab}{a}= \frac{a^{2}+b^{2}}{a}; \\ \\ \\ 124)..( \frac{2a}{a-b}+ \frac{a-b}{b})*b= \frac{(2ab+(a-b)^{2})b}{b(a-b)}= \\ \\ = \frac{2ab+a^{2}-2ab+b^{2}}{a-b}= \frac{a^{2}+b^{2}}{a-b}; \\ \\ \\ 125)..( \frac{1}{a-b}+ \frac{1}{b})* \frac{b}{a}= \frac{(b+a-b)b}{ab(a-b)}= \frac{1}{a-b};$

$\displaystyle 126)..( \frac{1}{y}- \frac{1}{x+y}): \frac{x}{y}= \frac{(x+y-y)y}{xy(x+y)}= \frac{1}{x+y}; \\ \\ \\127)..( \frac{1}{2a}+ \frac{1}{6a})* \frac{a^{2}}{4}= \frac{(3+1)a^{2}}{4*6a}}= \frac{a}{6};\\ \\ \\ 128)..( \frac{1}{5c}+ \frac{1}{10c})* \frac{c^{2}}{6}= \frac{(2+1)c^{2}}{6*10c}= \frac{c}{20}=0,05c; \\ \\ \\ 129)..( \frac{m+n}{m}- \frac{m+n}{n})* \frac{m}{m+n}= \frac{(nm+n^{2}-mn-m^{2})m}{mn(m+n)}= \\ \\ = \frac{(n-m)(n+m)}{n(n+m)}= \frac{n-m}{n};$