Question

Use factoring by difference of squares to solve the equation 4x^2 - 81 =0

Answer 1

what do you square to get 4x^2? How about 81? From there, it's easy...

Answer 2

4x and x is to the second power lol

Answer 3

check it out...

(a+b)(a-b) = a^2 + ab - ab - b^2 = a^2 - b^2 ... no middle term!!!

That's why it's called a difference of squares.

Answer 4

yes.. but what times itself gives you 4x^2?

Answer 5

idk it's on my questions and i thnk it's 2x times 2x

Answer 6

excellent!!!

That's it!

What about 81?

Answer 7

9 ?

Answer 8

OH so x = 2 or x = 9?? :D

Answer 9

perfect!!! you are pretty smart!

so let a = 2x and b = 9 up above...

Answer 10

(2x - 9)(2x + 9)! c:

Answer 11

nope, you've got to put them in the factors like I showed above.

(a + b)(a - b) = (2x + 9)(2x - 9)= 0

then just set each factor = 0 and solve for x.

Answer 12

you are ROCKIN!!!!

Answer 13

so +2/9 and - 2/9? :D

Answer 14

I mean the other way around haha, 9/2 and - 9/2? :)

Answer 15

close...

2x+9 = 0 => 2x = -9 => x = -9/2

likewise for the 2x-9 factor

Answer 16

dude... I mean dudette... you're so on top of this!!!

Answer 17

GREAT JOB!!!

Answer 18

Thank you so much!! I might need more help though with other things tho :O

Answer 19

You're welcome! I'll be here and I'll come see your questions. Don't hesitate to ask!

Answer 20

Thank you so much @pgpilot326

Answer 21

you're welcome!