Voltage in first order RC circuit
For questions like this, we prefer not to give complete solutions. Instead, we'd rather guide you to a solution so that you learn how to solve the problem yourself. So here's a couple of hints.

Hint: In the DC steady-state solution before the switch is opened, what is the relationship between \$v(t)\$ and \$v_1(t)\$?

Hint to the hint: In DC steady state, what is the current through the upper-right 2 kOhm resistor?