Question 377885
(5x^4) times (2xy - 9x^3) = 


Multiply (5x^4) by every term inside and add the exponents.


(5x^4) times (2xy) = 10x^5(y).


(5x^4) times (-9x^3) = -45x^7


We now put it all together.


10x^5(y) - 45x^7


Done!