(5x-5)*(x+4)

Question

What Is This Math Thing I don't know.

 

Answer 1

Hello, Hile!

 

(5x-5)*(x+4) is a multiplication problem.  It could be written (5x-5)(x+4) or (5x-5) x (x+4), though you almost never seen it written that last way.  To solve it, you use something called the FOIL method.  FOIL stands for First, Outside, Inside, Last and it is done as follows:

 

First:  5x * x = 5x²

 

Outside:  5x * 4 = 20x

 

Inside:  -5 * x = -5x

 

Last:  -5 * 4 = -20.

 

Add them all together and get 5x²+20x-5x-20.  Combine to get the answer of 5x²+15x-20.