00:01
Okay, the technique here is to multiply top and bottom with a conjugate of the bottom.
00:07
So, i times here and here quite the exact same thing.
00:12
That's 4 plus 3i, a complex conjugate.
00:17
There's no change overall.
00:20
And what happens now then, on top i will get 20.
00:25
Just do normal foil.
00:26
20 plus 15 i plus 4i is plus 19 i plus 3 i plus 3 i if i do i times 3 i on the bottom what happens i get 16 plus 12 i minus 9 i squared now, the key thing here is at 12i, that 12i cancel out, and i squared is negative 1.
01:08
I is the root of minus 1, so i squared negative 1.
01:14
So we get then 20, and then 3 i squared is minus 3.
01:20
So 20 minus 3, 17 plus the 19 i...