precalculus
posted by zana on .
$100,000 is divided into two investments with annual returns of 4% and 7.5%. find the amount invested at the lower rate if the total income at the end of the year is $5050?

amount invested at 4%  x
amount invested at 7.5%  100000x
solve for x:
.04x + .075(100000x) = 5050 
solve for x and express the solution in a+bi form : ix^23x+4i=0

You sure this is right?
ix^2  3x  4i = (ix+1)(x4i)
but that's not what we have.
So, using the good old quadratic formula,
x = (3 ± √5)]/2i