Hi,
Q2: The equation on the right is the numerator of the equation on the left.
Q3: j is the sqrt(-1), so j^2 is considered to be -1, and (-1)^2 is the same as j^4 so that equals 1.
Table:
j^1= j
j^2= -1
j^3= -j
j^4= 1
and for powers over 4 repeat the same pattern:
j^5=j^1= j
j^6=j^2=-1
j^7=j^3=-j
j^8=j^4=1
etc.
and note all we did was subtract 4 from the exponent repeatedly until the exponent is 4 or less. So:
j^9=j^(9-4)=j^5=j^(5-4)=j^1=j
and also for example j^15:
j^15=j^(15-4)=j^(11)=j^(11-4)=j^(7)=j^(7-4)=j^(3)=-j
Q4:
Take the transpose of the matrix and multiply by the matrix in that exact order, then calculate the inverse matrix.