The **energy** of the continuous-time signal x(t) is given by

**Note:** Here x(t) can be a real-valued signal or complex-valued signal.

The **energy** of the discrete-time signal x(n) is given by

**Note:** Here x(n) can be a real-valued signal or complex-valued signal.

The **power** of the continuous-time signal x(t) is given by

**Note:** Here x(t) can be a real-valued signal or complex-valued signal.

The **power** of the discrete-time signal x(n) is given by

**Note:** Here x(n) can be a real-valued signal or complex-valued signal.

**Note:** The signal whose energy is finite and power is zero is known as **energy signal**. The signal whose power is finite and energy is infinite is known as **power signal**. You can read more about the energy signal and the power signal here.

**Question: Compute energy of the following signal**

x(t) = e^{−t }u(t)

**Solution.** The energy of this signal is

So the energy of the signal x(t) is ½.

**Question: Compute energy of the following signal**

**Solution.** The energy of this signal is

The expression on the right-hand side is a geometric series; hence, we have

So the energy of the signal x(n) is 16/15.

**Question: Compute power of the following signal**

**Solution.** The power of this signal is

So the power of the signal x(n) is 1/2.