<p>So it says on the CollegeBoard Subject test:
4. If a and b are real numbers, i^2=-1 , and (a+b)+5i=9 + ai,what is the value of b ?
(A) 4
(B) 5
(C) 9
(D) 4 5 + i
(E) + 5 4i</p>
<p>now this confuses me, do we have some sort of plugging is system?
I tried doing that a+i= srt(a^2+i^2) but it just seems like a roundabout.
i though that...
srt[(a+b)^2+(5i)^2] = srt[9^2+(ai)^2]...
but is just goes round and round</p>
<p>can someone please help me?</p>
<p>thanks</p>