Answer:
4a^2-19ab-5b^2
Explanation:
What you do is the FOIL process.
F=First. The first thing that you do is times 4a and a together to get 4a^2.
O=Outer. You multiply the outer numbers 4a and -5b together to get -20ab.
I=Inner. You multiply the inner numbers b and a together to get ab.
L=Last. You multiply the last numbers b and -5b together to get -5b^2.
Put it all together to get 4a^2-19ab-5b^2 as your answer.