If you multiply these same base, add the exponent, you'll get i to the 99th power, i to the 96th power, so this is a multiple of 4, this is i to the 4th and then that to the 16th power, so that's just 1 in the 16, so this is just 1 and then you'll just lift with i to the third power and you could either remember that i to the 3th power is equal to... you could remember its equal to negative i or if you forget that you could just say look this is just samething as i squared times i, this is equal to i squared times i, i squared by definition is equal to negative 1 so you have negative 1 times i, is equal to i, is equal to negative i.