Prove the following:
zw* - z*w is purely imaginary or zero for all complex numbers z and w
A geometric series has a second term of 6 and the sum of its first three terms is -14. Find its fourth term.
Is it possible to bend a 20 cm length of wire into the shape of a rectangle which has an area of 30cm2?
Find the first two terms of an arithmetic sequence where the sixth term is 21 and the sum of the first seventeen terms is 0.