Question

Factor completely: 9x2 + 42x + 49

(3x + 7)(3x − 7)

(9x − 7)(9x − 7)

(3x + 7)(3x + 7)

(9x + 7)(9x + 7)

Please help it's 11:50 and my head is about to explode D:

Answer 1

Well at first sight, can't you right away eliminate B & D?

Answer 2

Do you know why?

Answer 3

I would, 3 hours ago but now no :(

Answer 4

hmm, okay making some sense.

Answer 5

Samw goes with choice D.
Since there are 9x and 9x; thus when you multiply them, you get 81x^2 not 9x^2 which is what you want.

Therefore: you want (3x + ?)(3x+?) or (3x + ?)(3x - ?)

Answer 6

*same

Answer 7

That leaves us to work with choice A & C

Answer 8

Ok, iv'e been trying to make sense of how to do this but I can't think straight, if it were an x2 + x + x it would be much easier

Answer 9

But are you understand better now? :)

Answer 10

yes it makes the question easier knowing I only have to distinguish one sign + or - :D

Answer 11

Okaii well lets continue then :)

Answer 12

alrighty

Answer 13

BTW do you know how to FOIL?

Answer 14

I know the basic yes

Answer 15

\[9x^2 + 42x + 49\]
So you need something like this:
Choice 1: (3x + ?) (3x + ?)
or
Choice 2: (3x + ?) (3x - ?)

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Now you need to find a number that when multiplied equals +49

Answer 16

1*49 and 7*7 is all I can think of

Answer 17

Okaii good good :)

so +7 and +7 is in one the choices =, right?

So it would be : (3x + 7)(3x + 7)

We can double check by FOIL

(3x + 7)(3x + 7) can also be written as (3x + 7)^2

Answer 18

I have to be seriously fried to not have realized this >_<

Answer 19

Thank you so much you have no idea how much you helped me :D