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1) \lim_{x\to\frac{\pi}{4}}\frac{1-\tan x}{\sin x-\cos x}&&2) \lim_{x\to-\infty} (\sqrt[3]{8x^3+2x^2+4}-2x)\nonumber\\
3) \lim_{x\to\frac{\pi}{3}^+}\frac{1}{2\cos x}&&4) \lim_{x\to+\infty}\frac{2^x+3^{2x-1}}{9^x+5^x}\nonumber
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