Question

find the product checking to see if I am close
(2r+4(2r-4)
4r^2-2r+8r

Answer 1

is that (2r+4)(2r-4)? if so, the answer is not as posted.

people use FOIL as a mnemonic, First , outer, inner last
first terms 2r*2r
outer 2r* -4
inner 4*2r
last 4*-4

put it all together and simplify

Answer 2

4r^2-6r
is that close sorry im trying here

Answer 3

because the 4*-4 cancel each other out correct

Answer 4

first terms 2r*2r = 4r^2
outer 2r* -4 -8r
inner 4*2r +8r
last 4*-4 -16

(2r+4)(2r-4)= 4r^2-8r+8r-16
-8r+8r =0 (you have 8 r's and take away 8 r's)
so the answer simplifies to
4r^2 - 16

notice that when you have the "same thing" except for + and - signs
(a+b)(a-b) the middle terms cancel. you get a^2 - b^2
or in this case 4r^2 - 16

Answer 5

ok so the final being the same thing cancels out the middle and the final answer is 4r^2-16 thank you for guiding me in the right direction this site rocks

Answer 6

here is a short video that makes it clear
http://www.khanacademy.org/math/algebra/polynomials/v/multiplying-binomials

Answer 7

thank you