Question

(5+4i)(17-13i)-(5+3i)(17-13i)

Answer 1

Use distributive property and multiply first
(85-65i+68i-52i^2)-(85-65i+51i-39i^2)
(85+3i-52i^2)-(85-14i-39i^2)  the subtraction sign applies to each part so
85+3i-52i^2-85+14i+39i^2  then add like terms
17i-13i^2

i^2 means i squared.