Use the distributive property and FOIL method After completing the multiplication replace i 2 with -1 4i(3-5i) (7-3i)(-2-5i)
For the complex conjugate a+bi, its complex conjugate is a-bi. The multiplication of complex conjugates results in a real number. (a+bi)(a-bi)=a 2 +b 2 (a-bi)(a+bi)=a 2 =b 2 The goal of the division procedure is to obtain a real number in the denominator. Example 7+4i 2-5i
The square root of 4i and-4i both result in -16. In the complex number system, - 16 has two square rolls, we use 4i as the principal square root.