Questions and Answers

Your Questions About X1

March 2, 2013

Thomas asks…

Does the Sony Ericsson Xperia X1 use a SIM card?

I want to know if the sony ericsson x1 uses a ssim card. if not, what networks does it support?

Administrator answers:


Mark asks…

How does the derivation of point slop form work?

I understand that the point slope form is derived from the slope formula, but I do not understand how it works. (y2-y1) / (x2 – x1) = m
How does y2 and x2 become the y and x in the equation y = mx + b

Administrator answers:

If you know two points on the line, P1:(x1, y1), and P2:(x2,y2) you can use those two points to define the slope as you have shown, (y2-y1) / (x2 – x1) = m

But that is only the first step in defining the line. The second step is to use one of the points, either one will work, but for illustration, let’s use P1. Substitute the selected point into the equation and solve for b

y1 = mx1 + b
b = y1 – mx1

So m = (y2-y1) / (x2 – x1)
and b = y1 – mx1
b = y1 – [(y2-y1) / (x2 - x1)]x1

and the point slope becomes:
y = [(y2-y1) / (x2 - x1)] x + {y1 – [(y2-y1) / (x2 - x1)]x1}
y = ……..m……………..x + ……………….b

Ruth asks…

What does a negative regressor mean in a regression estimation?

Say you have:

Y = -a + b1*X1 + b2*X2 + … + bp*Xp

How would you interpret -a in application? If for example Y = wage, then how could you have the possibility of a negative wage?

Administrator answers:

The “a” in the above equation is a little different than all the “b”s. The “a”s value is interpreted as the value for Y when all the X values are zero. Sometimes this value makes physical sense, sometimes it does not. A negative wage doesn’t really make sense, so it has no real meaning by itself.

Helen asks…

Dell support told me to get a PCI-E x1 video card, what does this mean?

I’m trying to get two monitors rollin’ on my dimension E3100 and Dell support told me I needed a PCI-E x1 video card. When I search for this on ebay I’m getting all sorts of stuff; motherboards, computers, etc., and I just need the card! Do I basically just need a dual PCI card?
Thanks everybody….maybe I should have included something, I’m not a gamer, and I’d be using this mainly for browsing the web and watching an occasional movie/show, and having the best of the best picture isn’t #1 on my list. So the simpler/cheaper, the better.

Administrator answers:

Try one of these:

HIS Hightech H130HMF128E1N Radeon X1300 512MB HyperMemory with 128MB Onboard 64-bit GDDR2 PCI Express x1 Low Profile Video Card – $69.99

HIS Hightech H130HMF128E1N Radeon X1300 512MB HyperMemory with 128MB Onboard 64-bit GDDR2 PCI Express x1 Low Profile Video Card – $96.99

Be sure to read the reviews.

Good luck and Happy Computing!

Paul asks…

How do you solve this question on statistics?

The standard deviation of the set of data x1,x2,x3,…,xn is 2 .
For the set of data 3(x1) – 5, 3(x2) – 5, 3(x3) – 5, …, 3(xn) – 5, find the new variance.

Administrator answers:

Calling X the array of data whose standard deviation is 2
var(x) = sqrt(2)

var(3X – 5) = 3^2 var(x) + 5

var(3X – 5) = 9sqrt(2) + 5

Carol asks…

How do I build shoes that can walk on water?

I have this idea to use hard foam probably around 5′x15″x1‘ to craft a shoe that will hope fully be able to float and hold 100 lb. I will be hollowing it out so that my foot will fit in and I will be cutting some away so that it is not just a block sitting in the water. Will this work?
If it does how can I make it better?
If it doesn’t how can I make it work?

Administrator answers:

Water weighs 62 pounds per cubic foot so you theoretically only need to displace 2 cubic feet to float
Your main problem will be stability, the shoes will want to flip over and suspend you upside down in the water

If you make the shoes shorter and wider, say 4 feet long by 2 feet wide then join them so they stay together but can slide forward and back 1 foot independently they might be more stable. You will also need ridges underneath, like a large ripple sole with a sloping forward surface and a 90 degree rear surface to give you a bit of traction in the water.

4 foot long and 4 inch wide outriggers 6 feet apart on a U- shaped pole might assist with you staying upright

Lizzie asks…

How many nonnegative integer solutions are there to the pair of equations?

a.How many nonnegative integer solutions are there to the pair of equations x1+x2+x3+…..+x7=37, x1+x2+x3=6?
b. How many solutions in part (a) have x1,x2,x3>0?

Administrator answers:

A) Since x1+x2+x3 = 6, the first equation reduces to x4+x5+x6+x7 = 37 – 6 = 29.

X1+x2+x3 = 6 has C(6 + 2, 2) nonnegative integer solutions (combination with repetition, 6 ‘stars’ and 2 ‘bars’), while x4+x5+x6+x7 = 29 has C(29 + 3, 3) nonnegative integer solutions.

So, the original system has C(6 + 2, 2) * C(29 + 3, 3) solutions.
b) Note that counting the solutions to x1+x2+x3=6 with x1, x2, x3 ? 1 is equivalent to
counting the solutions to x1+x2+x3 = 6 – 3 = 3 with x1, x2, x3 ? 0.

Since this now has C(3 + 2, 2) solutions, the original system now has
C(3 + 2, 2) * C(29 + 3, 3) solutions.

I hope this helps!

Charles asks…

How do you convert slope intercept and slope point forms to general (standard) form?

Slope intercept form: Y = MX + B

Slope point form: Y – Y1 = M(X – X1)

General (standard) form: A + B + C = 0
Frank: You think posting a question on Y!A was my first solution? Don’t post an answer unless you actually intend to help someone with their problem, jerk.

Administrator answers:

General (standard) form is actually Ax + By + C = 0

So for Slope Intercept Form to General (standard) Form, it’ll be something like this:
Y = Mx + B is the same as By = Ax + C
Then subtract By from both sides to get the General (standard) Form
Ax – By + C = 0
y = 4x + 17 <– Slope Intercept Form
subtract y from both sides
4x – y + 17 = 0 Y – 1 = 4/9(X – 6)
Distribute and all that to get:
Y = 4/9X – 5/3
Then subtract Y from both sides
4/9X – Y – 5/3 = 0
And since General (standard) Form is always in whole numbers, we have to get rid of all the fractions
4X – 9Y – 45/3 = 0 <– I multiplied everything by 9
12X – 27Y – 45 = 0 <– then I multiplied everything by 3

I hope I helped! ^^

Sharon asks…

Calculate the partial derivatives of each of the following functions with respect to x1 and x2?

F(x1,x2)=lnx1 + x2^-1 = 1/x1

I would like to know if it is the right answer its been a while I have’nt done any partial derivatives ,what is the deffirent with just derivatives.
1/x1 is an answer I got by calculating the partial derivatives with respect to x1

Administrator answers:

I’m going to assume that you have a typo in your expression for F, and that it should be

F(x1, x2) = ln(x1) + (x2)^(-1) + 1/x1

?F/?x1 = 1/x1 -1/(x1)²
?F/?x2 = -1(x2)^(-2)

When you compute a partial derivative, say, with resepct to x1, you treat all other variables as if they were constants.

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