1. SOLUTION:[tex]\begin{aligned} a_n & = a_1 + (n - 1)d \\ & = 50 + (n - 1)(50) \\ & = 50 + 50n - 50 \\ a_n & = \boxed{50n} \end{aligned}[/tex]2. SOLUTION:[tex]\begin{aligned} a_n & = a_1 + (n - 1)d \\ & = 5 + (n - 1)(2) \\ & = 5 + 2n - 2 \\ a_n & = \boxed{2n + 3} \end{aligned}[/tex]3. SOLUTION:[tex]\begin{aligned} a_n & = a_1 + (n - 1)d \\ & = 40,000 + (n - 1)(2,000) \\ & = 40,000 + 2,000n - 2,000 \\ a_n & = \boxed{2,000n + 38,000} \end{aligned}[/tex]