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+118725

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You can not find the square root of a negative number. There is no answer.
(not in the real world anyway)

MelodyNov 3, 2013

+118725

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Hi TG,
This is an interesting little question!

"At 7 am Brooke leaves home to go on a business trip driving 35 miles per hour. Fifteen minutes later, Bart discovers that Brooke forgot her presentation materials. He drives 50 miles per hour to catch up with her. If Bart is delayed 30 minutes with a flat tire, when will he catch up with Brooke"

Let the distance travelled by X. This is the same for both of them.
Let T= time that Brooke travels (in hours)

Your first question is:
If Brooke travels for T hours, how long does Bart travel for (in hours)?

You have to set up an equation for Brooke and another equation for Bart

Use speed=distance/time, except you will want distance to be the subjsect of both fromulas

Now solve them simultaneously to find T

Is that enough help?

MelodyNov 3, 2013

+22

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Yes you did do that correctly towards the end, but that first bit had nothing to do with the question. What you did in the beginning is what you would do if you were trying to find the mass of 1.5mol of fluorine, not the number of atoms.

CyphersumNov 3, 2013

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GuestNov 3, 2013

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GuestNov 3, 2013

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You mean slope? Slope is a line represented by a function like y=mx+b, or it could be a fraction. You can graph slope on a graph. Slope is always linear.

GuestNov 3, 2013

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GuestNov 3, 2013

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hi Tupu, what school do u go to? I have an exam on that on Tue.
Hope I can help:
use the formula
n=m/M
n=moles (first find for 1 mol)
m=mass
M=molar mass (in this case F:19)
1mol= x g / 19g/mol
you can then rearrange the equation so that it's m=Mn : m=1(19) => m= 19g
in 1.5 mols there are: 1mol=19g
1.5 mol= ? ,1.5 mol= 28.5g
In 1 mol there are 6.02*10²³ atoms so your conversion-factor is 1/ 6.02*10²³
Now, I'm slightly confused because that would mean I'm disregarding my previous steps, but then what I would do is:
1.5mol * 6.02*10²³/mol (now the moles cancel and what you get is that there are 9.03*10²³ atoms in 1.5 moles of flourine gas...)
did this help? was I somewhat correct? By answering that you'd be helping me in my Exam!!!! Thx

GuestNov 3, 2013

+118725

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Translation

How to convert large number in small one to two digit
How to convert a huge number in the equivalent of one or two digits?

Can you give a example of what you want to do ?
Make sure there are numbers in your example.

Pode dar um exemplo do que você quer fazer?
Certifique-se que existem números no seu exemplo.

MelodyNov 3, 2013

+118725

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X/3-1/2=x/5+ 3/2

The lowest common denominator is 2*3*5 = 30
multiply both sides by 30 (use brackets)
That will get rid of all the fractions and then hopefully you will be able to do it yourself.

MelodyNov 3, 2013

+118725

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Solve 2(Sec x)^2=5tanx-1

I tried the usual method and it didn't work for me so I decided to get a bit inventive.

I said, let t=tanx
now you can draw a right angled triangle and let x be one of the acute angles.
let 't' be the opposite side and 1 be the adjacent side.
Now you have a triangle where tanx = t
Use pythagoras to get the hypotenuse = Sqr(1+t^2)

So now sec x = [ Sqr(1+t^2) ] / 1

2sec^2 x = 2(1+t^2)
So
2(1+t^2) = 5t - 1
rearrange and factorise and you get
(2t-3)(t-1) = 0
so t = 3/2 or t = 1
t=tanx

If t=1 then x = pi/4 +- n*pi Where n is an integer

If t=3/2 then x = atan(3/2) +- n*pi

Hence
x = pi/4 +- n*pi OR x = atan(3/2) +- n*pi Where n is an integer (atan stands for arc tan which is the same as inverse tan)

I did consider this a little more, sometimes 1 or more of answers gained like this can be wrong because of negative signs (you do need to be careful) but
2(Sec x)^2 +1 is always going to be positive so x needs to be in the 1st or 3rd quadrant so I don't think there is any need to be concerned.

MelodyNov 3, 2013

+118725

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Solve 2Sec^2=5tanx-1
I assume you meant

Solve 2(Sec x)^2=5tanx-1

It's got me stumped too for the moment. But I am still playing with it.

MelodyNov 3, 2013

+118725

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A circle has a diameter of 20 cm.
The line AC is a diameter of the circle.
B is a point on the circumference of the circle with AB = 12 cm. The point D lies on the arc AC on the opposite side to point B.
What is the sine of ∠BDC?

<BDC=<BAC they are both subtended from arc BC so they are congruent

<ABC = 90degress (angle in a semicircle)

Cos(<BAC) = 12/20

and you can finish it.

MelodyNov 3, 2013

Nov 2, 2013

+118725

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Anything divided by itself = 1 (except 0)

MelodyNov 2, 2013

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put the parenthesis and then the numerator divided by the denominator and end the parenthesis.
example: (1/2)

GuestNov 2, 2013

+118725

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890+4 3/4 = 894 3/4

MelodyNov 2, 2013

+118725

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Not to worry, I make embarassing mistakes all the time.

MelodyNov 2, 2013

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I knew that. I'd rather not say how I got that. I now realise my embarassing mistake.
Thanks!

GuestNov 2, 2013

+118725

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What are the dimensions of a prism that has a volume of 216mm3 but is not a rectangular prisim

As you are probably aware, there are many answers to this problem.

It could be a triangular prism where : 1/2 * base * height * length = 216
OR
It could be a cylinder where : pi * r^2 * height = 216
Or
any other shape prism where 216 = area of front face * depth

MelodyNov 2, 2013

+118725

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Just remember that multiply and divide are done before plus or minus

7 - 4 + 3 x 0 + 1

= 7 - 4 + (3 x 0) + 1

=7 - 4 + 0 + 1

= 4

How did you get 2 ??

MelodyNov 2, 2013

+118725

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1) -6 - -5 - 8 =
2) -5 x -6 x -2 =
3) 8 divided by -4 x -5=

http://www.youtube.com/watch?v=d8lP5tR2R3Q

There is one clip for adding and subtracting
and
another for multiplying

see if these help you.

MelodyNov 2, 2013

+2

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Good job,I appreciate your work.

romanoprodiNov 2, 2013

+118725

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First simplify both sides separately. Which means expand the bracket and collect like terms.
If you have a go at this and don't know what to do next then you can post again.

MelodyNov 2, 2013

+118725

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What is the squareroot of 12

sqr12 = sqr4 *sqr3 = 2*sqr3

Or, you can get an estimate from your calculator.

MelodyNov 2, 2013

+118725

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Pour la physique j'ai à résoudre se calcul : 2.657x10^(-26)/1.673x10^(-27) et je trouve la bonne reponce mais avec a peu près 52 zeros donc je ne trouve pas comment simplifier pourriez vous m'aidez ?
merci

For physics I have to solve is calculation: 2.657x10^(-26)/1.673x10^(-27) and I find the good answer but with about 52 zeros so I can not find how to simplify pourriez you help me?
Thank you

2.657x10^(-26)/1.673x10^(-27) = (2.657 / 1.673 ) * 10^(-26 - - 27) = 1.588 * 10^1 = 15.88 ( to 3 significant figures ) (à trois chiffres significatifs)

OR you could just do the whole lot on your calculator
OU vous pourriez juste faire le tas sur votre calculatrice

2.657 EXP -26 / 1.673 EXP -27 =

MelodyNov 2, 2013

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