Question

пожайлуста помогите!!!

Answer 1

$displaystyle 15.9)..(frac{a}{6}- frac{6}{a})*( frac{1}{6+a}+ frac{1}{6-a})= frac{a^{2}-36}{6a}* frac{6-a+6+a}{36-a^{2}}= \ \ \ = -frac{36-a^{2}}{6a}* frac{12}{36-a^{2}}= -frac{2}{a}; \ \ \ 15.10)..( frac{a-8}{a+8}- frac{a+8}{a-8}): frac{16a}{64-a^{2}}= frac{(a-8)^{2}-(a+8)^{2}}{a^{2}-64}* frac{64-a^{2}}{16a}= \ \ \ =- frac{(a-8+a+8)(a-8-a-8)}{64-a^{2}}* frac{64-a^{2}}{16a}= frac{2a*16}{16a}=2;$

$displaystyle 15.11)..( sqrt{7-4 sqrt{3}}+ sqrt{7+4 sqrt{3}}})^{2}= \ \=( sqrt{7-4 sqrt{3}})^{2}+2* sqrt{49-48}+( sqrt{7+4 sqrt{3}})^{2}= \ \ =7-4 sqrt{3}+2+7+4 sqrt{3}=16; \ \ \ 15.12)..-3,25 leq frac{1-4x}{3} textless 1,25 \ \-9,75 leq 1-4x textless 3,75 \ \1-4x geq -9,75 \ -4x geq -10,75 \ x leq 2,6875 \ \ 1-4x textless 3,75 \ -4x textless 2,75 \ x textgreater -0,6875$

При х∈Z:   x = {0; 1; 2}