find the product (j + 7)(j – 7)

Question

find the product of (j + 7)(j – 7)

Answer 1

(j+7)(j-7)

=j*j+j*-7+7*j+7*-7

=j^2-7j+7j-49

=j^2-49

this is the difference of 2 squares (j^2-7^2)

Answer 2

j^2-7j+7j-49

Answer 3

j^2-7j+7j-49

j^2-49

Answer 4

If j=√-1, then (j+7)(j-7)=j²-49=-50.

(In engineering j is often used to represent the imaginary √-1, which is also represented by i.)