How do you simplify #( 3 + i ) ( 3 + i )#? Precalculus Complex Numbers in Trigonometric Form Multiplication of Complex Numbers 1 Answer Topscooter Jan 8, 2016 #8+6i# Explanation: It is the known square #(a+b)^2#. So you apply its formula to this complex number. #(3+i)(3+i) = (3+i)^2 = 3^2 + 2*3i+i^2 = 9 + 6i - 1 = 8+6i# Answer link Related questions How do I multiply complex numbers? How do I multiply complex numbers in polar form? What is the formula for multiplying complex numbers in trigonometric form? How do I use the modulus and argument to square #(1+i)#? What is the geometric interpretation of multiplying two complex numbers? What is the product of #3+2i# and #1+7i#? How do I use DeMoivre's theorem to solve #z^3-1=0#? How do I find the product of two imaginary numbers? How do you simplify #(2+4i)(2-4i)#? How do you multiply #(-2-8i)(6+7i)#? See all questions in Multiplication of Complex Numbers Impact of this question 1447 views around the world You can reuse this answer Creative Commons License