問題：次の式を計算せよ

• (1) \( \displaystyle \lim_{x \to 2} (x^2 + 5x) \)


• (2) \( \displaystyle \lim_{x \to +1} \dfrac{5}{x - 1} \)


• (3) \( \displaystyle \lim_{x \to 1} \dfrac{x-1}{x^3 - 1} \)


• (4) \( \displaystyle \lim_{x \to 8} \dfrac{4x + 3}{2\sqrt{x + 1} + 1} \)


• (5) \( \displaystyle \lim_{x \to \infty} \dfrac{8x^2 + 1}{2x^2 + 4x + 5} \)