Can someone show me the answer + how they got there? (x+4)(x-1)

Explanation:

You can use the FOIL rule to expand out (x+4)(x-1), but here's another way you could do it.

Let y = x+4

This means we replace (x+4) with y to get y(x-1)

Distribute the y term through to get yx-y which can be written as x(y) - 1(y)

After this, replace y with x+4 getting x(x+4)-1(x+4)

Distribute a second time and simplify like so

x(x+4)-1(x+4)

x^2+4x-1x-4

x^2+3x-4