expand:(x+2)(x-8)

Question

a. xsquared+6x-16

b. xsquared-6x+16

c. xsquared-16

d. xsquared-6x-16

Answer 1

Hi there!

Okay I like the explanation by Mr. Bill and I want to present another way of doing it that is just as good just so that you know there's more than one way to expand a product of binomials:

Step 1: Multiply the first x by (x - 8) and multiply the 2 by (x - 8), then join these with a plus sign .

                                       (x + 2)(x - 8)

                                    x(x - 8) + 2(x - 8)

Step 2: Multiply the x through and the 2 through.

                                    x(x - 8) + 2(x - 8)

                                    x*x - 8*x  + 2*x - 2*8

Step 3: Simplify each term

                                    x*x - 8*x  + 2*x - 2*8

                                    x² -8x + 2x - 16

Step 4: Last, combine like terms

                                    x² - 6x - 16

Answer 2

This quadratic equation can be solved in several ways.  One that to me seems the simplest is known as  FOILing the equation.  This method takes advantage of the distributuve property of math to solve an equation.

Multiply together the first two knowns and variables in each expression (F).  In this case that would be X x X= X^2.  (This is an expression and not an equation because it is not set to an equal sign)

Now multply together the outside knowns and variables (O) X x -8= -8x.

Next multiply together the inside knowns and variables (I) 2 x X= 2x.

Now, multiply the last two knowns and variables (L) 2 x -8= -16

So when you combine these you get x^2 - 8x + 2x - 16

Last, combine like terms and presto you have x^2 - 6x - 16