Answer: 8x^2 - 15^2 + xy
Explanation:
expand brackets by multiplying
(4x+5y)(2x-3y)+3xy
8x^2 - 12xy + 10xy - 15y^2 + 3xy
collect like terms
8x^2 - 15y^2 -12xy + 10xy + 3xy
solve
-12xy + 10xy + 3xy
=1xy (note: when writing/typing the answer, don't add 1 in front of the xy.)
final answer: 8x^2 - 15y^2 + xy