Question

What is the product of (2+7i)(2-7i) in the from a+bi

Answer 1

I = sqrt(-1), i^2 = -1

So multiplying it out;

4 - 14i + 14i - 49i^2

4 - 49 * -1

= 53

Answer 2

Answer:

Step-by-step explanation:

(2+7i)(2-7i)  =  2² - (7i)²              { ( a+b) (a-b) = a²-b² }

                  = 4 - 7² * i²

                    = 4 - 49* (-1)

                     = 4 + 49

                     = 53