Question

помогите с 12
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Answer 1

$frac{a^2-4b^2}{2ab}:(frac{1}{2b}-frac{1}{a})=frac{(a-2b)(a+2b)}{2ab}:frac{a-2b}{2ba}=frac{(a-2b)(a+2b)}{2ab}cdot frac{2ab}{a-2b}=\\=a+2b=5 frac{11}{7}+2cdot 7 frac{3}{17}=frac{46}{7}+frac{2cdot 122}{17}=frac{46cdot 17+7cdot 244}{7cdot 17}=\\=frac{2490}{119}=20 frac{110}{119}$