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.

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


How do I integrate (sin x)^6?


How do you sketch the graph of y=(x-1)/(x+1)?


Let E be an ellipse with equation (x/3)^2 + (y/4)^2 = 1. Find the equation of the tangent to E at the point P where x = √3 and y > 0, in the form ax + by = c, where a, b and c are rational.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo
Cookie Preferences