please help! alg 2

We can turn this problem into a subtraction problem:  (2+7i) - (3-5i). 

Since the order of subtraction/addition problems don't matter (a+b=b+a and a-b=-b+a), we can turn the problem into: (2-3) + (7i - -5i)

Subtracting a negative number is like adding the positive version of it: (2-3) + (7i+5i)

Doing the parts individually, 2-3 = -1 and 7i+5i = 12i.

Finally, we can combine them and our solution is -1 + 12i or 12i - 1. 

I hope this helped :)

What number must we add to 3-5i  to get 2+7i ? Here, i^2=-1

3+ -1=2

-5+ 12 = 7

so the answer is     -1+12i

For addition and subtraction you can treat the i like it is just an ordinary pronumeral.