A complex number is a special type of number that takes the form of a + bi, where i is the symbol for the square root of -1. Can you figure out two complex numbers (where neither a nor b is zero) that when multiplied together become a real number? 
 
 
How would I solve 2i/(1+i) ?
 I know the answer is 1+i but I don't know how to get there.
 
 
How would I find the quadratic equation given the solutions of ± i?
 
 
Why do you multiply both the numerator and the denominator of the quotient by the complex conjugate ?
 
 
How do you divide this: 4/(7 + 2i)?
 
 
I am stuck on solving the problem below, writing the answers in standard form of a complex number, can you also show how it is worked out, thanks in advance.
(-2 + 5i) (i - 4) =

 
 
What is  √(-9) in terms of i?