Question 274218
Multiplying polynomials is like a playing in a round-robin tournament, that is, everyone on one team multiplies everyone on the other team...sooooo....

Multiply 4x times (2x-3u-4) and get 8x^2 - 12ux - 16x   then
multiply +u times (2x-3u-4) and get 2ux - 3u^2 - 4u   then
multiply -4 times (2x-3u-4) and get -8x + 12u + 16

Now collect like terms and get

8x^2 - 3u^2 - 10ux - 24x + 8u + 16