Find the absolute value of the complex number 5 - 4i. a. -6.4 c. 6.04 b. 6 d. 6.4 select the best answer from the choices provided last question giving 50 easy points!

I answered a similar question for someone else. The absolute value of a complex number is called the modulus. This represents the DISTANCE to the origin from the point on the imaginary + real plane. 
the real horizontal distance is 5 and the imaginary vertical distance is in this case 4 (from -4i) the distance is 4. So to figure out this just use the Pythagorean theorem.
5^2 + (4)^2 = c^2 
25 +16 = c^2 
c^2 = 41c = 6.4 So option D.