Posted by
anonymous on
.
solve c(x)=x^240x+405

Math 
Henry,
C(x) = x^2  40x + 405 = 0,
Use the Quadratic Formula:
x = ( 40 + sqrt(4001620)) / 2,
x = (40 + sqrt(20)) / 2,
x = (40 + sqrt(20*1)) / 2,
x = (40 + 4.47i) / 2,
Solution Set:
x = 20 + 2.24i.
x = 20  2.24i.

Math 
Henry,
Correction:Replace 400 with 1600.