# Math Help - pygoream theorem 8th grade math.

1. ## pygoream theorem 8th grade math.

ok, i dont know if im doing this right so i just need it checked by someone who is familiar with the subject.

http://img180.imageshack.us/img180/2673/30971384nh8.jpg

I'm not sure im doing it right, and since X=47 does that mean the red car's speed is 47miles per hr?

2. Originally Posted by zombie
ok, i dont know if im doing this right so i just need it checked by someone who is familiar with the subject.

http://img180.imageshack.us/img180/2673/30971384nh8.jpg

I'm not sure im doing it right, and since X=47 does that mean the red car's speed is 47miles per hr?
just wanted to say in the picture i forgot to put the 5x Squared and if anyone answers my question can they teach me how to put square root symbols and stuff in forum posts.

3. Bump

4. Originally Posted by zombie
using the theorem we get...

$(2x)^2+x^2=(105)^2 \iff 4x^2+x^2=(21 \cdot 5)^2$

$5x^2=(21 \cdot 5)^2 \iff x^2=5 \cdot (21)^2$

taking the square root of both sides

$x= \pm 21\sqrt{5} \approx \pm 46.96$

We want only the positive root

Good luck.

as for the La tex try this link

http://en.wikipedia.org/wiki/Help Formula

5. yeap, thats what i got for the 46.96, and i rounded it off to 47. But since
x=47 that means the red car's speed is 47 m/hr? Or do i have to times it by two since the word problem says that "the red car's speed is twice the blue car's speed" or do i divide 47 by half to get the speed of the blue car.

6. Originally Posted by zombie
yeap, thats what i got for the 46.96, and i rounded it off to 47. But since
x=47 that means the red car's speed is 47 m/hr? Or do i have to times it by two since the word problem says that "the red car's speed is twice the blue car's speed" or do i divide 47 by half to get the speed of the blue car.
In the original we had each velocity as x and 2x and we solved for x so the rate of the faster car will be 94

7. ok i get it now. i did everything you did except where you took (21 X 5)squared
I just took the 105 and squared it, combined the like terms, isolated X by divining both sides by 5 and then finally took the square root of both sides to get the X squared alon and ended up with the rounded off 47. Thanks alot.