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

2270 Views

See similar Further Mathematics A Level tutors

Related Further Mathematics A Level answers

All answers ▸

Find the area of the surface generated when the curve with equation y=cosh(x) is rotated through 2 pi radians about the x axis, with 2<=x<=6


Integrate (x+4)/(x^2+2x+2)


Find the general solution of the differential equation d^2y/dx^2 - 5*dy/dx + 4y = 2x


You are given a polynomial f, where f(x)=x^4 - 14x^3 + 74 x^2 -184x + 208, you are told that f(5+i)=0. Express f as the product of two quadratic polynomials and state all roots of f.


We're here to help

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

MyTutor is part of the IXL family of brands:

© 2026 by IXL Learning