Expand and simplify (x-5)(x 4)

We need to multiply both parts of each bracket by the both parts of the other bracket: we have 2 brackets with 2 parts each, so we will have 4 expressions now:

x*x; -5x; 4x; -20

now we add them:

x*x+( -5x)+ 4x+( -20) - this is the expanded expression.

Now, let's simplify:

x*x-5x+ 4x -20=

x*x-x -20=