Limit at Infinity with Roots

Evaluate a) limx5x243x19x\displaystyle\lim_{x\to\infty}\frac{\sqrt{5x^2-4}-3x}{1-9x} and b) limx5x243x19x\displaystyle\lim_{x\to-\infty}\frac{\sqrt{5x^2-4}-3x}{1-9x}.

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