Evaluate the following product of two complex numbers: (3+4i)*(2-5i)

Answer : 26-7iMethod : Expanding the brackets will result in the sum, 6 -15i + 8i - 20i2by assessing this you can see that you can evaluate -15i + 8i to be equal to -7i which is the imaginary part of the complex number, one bit of the real part comes from the product of the real parts of each of the complex numbers (2*3 = 6) but from the properties of the imaginary constant i, the remainder of the real part comes from the i2 term which of course evaluates to -1. Hence -20i2 is equal to 20 and the real part is then equal to 26. Therefore, the product is equal to 26-7i.

CB
Answered by Christopher B. Further Mathematics tutor

1773 Views

See similar Further Mathematics A Level tutors

Related Further Mathematics A Level answers

All answers ▸

Find a vector that is normal to lines L1 and L2 and passes through their common point of intersection where L1 is the line r = (3,1,1) + u(1,-2,-1) and L2 is the line r = (0,-2,3) + v(-5,1,4) where u and v are scalar values.


Could you explain to me how proof by induction works?


prove by induction that, f(n) = 2^(3n+1) + 3(5^(2n+1)) is divisible by 17 for all n>0.


The rectangular hyperbola H has parametric equations: x = 4t, y = 4/t where t is not = 0. The points P and Q on this hyperbola have parameters t = 1/4 and t = 2 respectively. The line l passes through the origin O and is perpendicular to the line PQ.


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences