# how to find an equation given something

#### alessandromangione

if i= square root of -1, then -4i (6i ) is...

#### spruancejr

Let's review the properties of i:

$$\displaystyle i = sqrt (-1)$$
$$\displaystyle i^2 = -1$$
$$\displaystyle i^3 = -i$$
$$\displaystyle i^4 = 1$$

each set of i iterates in this fashion which means
$$\displaystyle i^5 = sqrt(-1)$$

alessandromangione