FOlL is really just using the distributive property twice so, for example, you take this expression, whatever you have out here if you had a 9 out here or an "a" or an "x" or anything, now you have 7x minus 5 if your multipling it times this expression you would multiply this times each term over here so when you multuply 7x minus 5 times x to the third you get, and i'll write it this way, you get x to the third times, acutally let me write it the other way you get 7x minus five times x to the third and then you have plus 7x minus 5 times 4x and now we can do the distributive property again we're not normally used to seeing the things we distributed on the right hand side but it's the same exact idea. we could put x to the third here as well now when we distribute, you multiply x to the third times 7x and times negative 5 x to the third times 7x is 7x to the fourth power x to the third times negative 5 is minus 5x to the third and then you do it over here, you distribute the 4x times 7x is plus 28x squared 4x times negative 5 is minus 20x and lets see if we can simplify this we only have one fourth degree term, one third degree term, one second degree term, and one first degree term so actually you can't simplify this anymore and we're done! this is the product of those two function definitions this is f times g of x. it is a new function created by multiplying the other two functions.
FOIL หมายถึงการใช้สมบัติการกระจายสองครั้ง ตัวอย่างเช่น, คุณเอาเทอมนี้มา, ไม่ว่าคุณจะมีอะไรตรงนั้น ถ้าคุณมี 9 ตรงนี้ "a" หรือ "x" หรืออะไรก็ช่าง, ทีนี้คุณมี 7x ลบ 5