Question

Multiply: (3a + 11)(3a - 11)
im having trouble with these stuff. i get it and everything i just got confused and i dont know if i got the right answer. i think the right answer is 9a^2 -121. Is it wrong?

Answer 1

As I said in the last post - \((a + b)(a - b) = a^2 - b^2\)
Here it'd be \((3a + 11)(3a - 11) = (3a)^2 - (11)^2\)

Answer 2

http://openstudy.com/updates/4fd62be0e4b04bec7f17374c See this tutorial by me, this may help. :)

Answer 3

\[9a^2 - 121\] is the right answer...

Answer 4

if you doubt then go back to good old FOIL :)

(3a x 3a) + (3a x -11) + (11 x 3a) + (11 x -11)

9a^2 - 33a + 33a - 121

9a^2 - 121! :D

Answer 5

do FOIL! ....first outside, inside, last.

9a^2 - 33a + 33a - 121 then simplify it to

9a^ 2 - 121