(5+4i)(17-13i)-(5+3i)(17-13i)
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 so85+3i-52i^2-85+14i+39i^2 then add like terms17i-13i^2i^2 means i squared.