Symbol i we call imaginary unit =>
This is basic
i^2= i * i = -1
i^3= i^2 * i = -1 * i = - i
i^4= i^3 * i = -i * i = - (i * i )=- (i^2)= - (-1) = 1
i^5= i^4 * i = 1 * i = i
i^6= i^5 * i = i * i = i^2 = -1
i^7= i^6 * i = -1 * i = - i
i^8= i^7 * i = -i * i = -(i * i)= -( i^2)= - (-1) = 1
You have all you need.
You conclude which simplifications of the power i are correct.
Good luck!!!!
