1. ## expanding brackets

Hi what is (3x + 1/x)^2 ???????

2. Originally Posted by wolfhound
Hi what is (3x + 1/x)^2 ???????
HINT: (a + b)^2 = (a + b) times (a + b)

3. Originally Posted by Wilmer
HINT: (a + b)^2 = (a + b) times (a + b)
I know that

4. Hi!

One should lnow the binimial theorems

$(a+b)^2 = a^2 + 2ab + b^2$

$(a-b)^2 = a^2 - 2ab + b^2$

$(a+b)(a-b) = a^2-b^2$

In the example it is a = 3x and b = 1/x

Can you solve it now?

Edit

Originally Posted by wolfhound
I know that
Okay, here is the solution

(3x)^2+2*(3x)*(1/x)+(1/x)^2

$= 9x^2+\frac{6x}{x} + \frac{1^2}{x^2}$

$= 9x^2 +6 + \frac{1}{x^2}$

5. I know all that pascals triangle stuff ,what I dont understand is what becomes of 3x when its multiplied by 1/x?? or 1/x x 1/x?

6. Okay, here is the solution

(3x)^2+2*(3x)*(1/x)+(1/x)^2

$= 9x^2+\frac{6x}{x} + \frac{1^2}{x^2}$

$= 9x^2 +6 + \frac{1}{x^2}$[/QUOTE]

thanks

7. Originally Posted by wolfhound
I know all that pascals triangle stuff ,what I dont understand is what becomes of 3x when its multiplied by 1/x?? or 1/x x 1/x?
$(3x)(\frac{1}{x})= \frac{3x}{x}= 3$

$(\frac{1}{x})(\frac{1}{x})= \frac{1}{x^2}$