Thursday

October 23, 2014

October 23, 2014

Total # Posts: 94

**Algebra 2**

differentiate y with respect to x (dy/dx). That gives you the slope at any point on the graph. The slope is always 0 at the max and min points so put dy/dx = 0 and solve for x. Once you get that value of x put it back into y to find the corresponding y value for the minimum ...
*October 22, 2014*

**Physic**

Cliff height is correct Max height is correct (I got 29.7m) Ball's impact speed isn't right. you need to find Vx and Vy at time 3.3s Vx = Ux - 0*t (gravity doesn't act in the horizontal direction) Vy = Uy - g*t (gravity acts downwards so -ve g) So we get Vx = Ux = ...
*October 22, 2014*

**math**

Not C either. 10^2 + 7^2 = hyp^2 Find the hyp from that
*October 22, 2014*

**math**

41^2 = 40^2 + x^2 1681 = 1600 + x^2 81 = x^2 9 = x
*October 22, 2014*

**math**

Careful Brady. In this question it's 41^2 = 40^2 + x^2
*October 22, 2014*

**math**

Afraid not.
*October 22, 2014*

**Science ONE QUESTION!**

Spot on :)
*October 22, 2014*

**Science ONE QUESTION!**

Ok, so if it was 100 kg m/s before then according to the conservation of momentum it must be...
*October 22, 2014*

**guidance**

Discipline could have the opposite effect. Choices is the correct answer. By making your own decisions you take ownership of them and shape your life. Constant care can make you overly reliant on others.
*October 22, 2014*

**Math**

vol of a sphere = (4/3)*pi*r^3 = 2404*pi find r from that. The length, width and height of the box around the sphere will be the diameter of the ball. Diameter = 2r Area of box = 6*(2r)^2 = 24r^2 cm2 (6 identical faces of area 2r*2r)
*October 22, 2014*

**Math**

Well, what % of is money does he have now? i.e. what percentage does $120 equal? What percentage do you want? You'll get something that looks like this example: 10% = $70 (what you were given) 50% = ? (what you want) What would 50% be in dollars in that example? See if you...
*October 3, 2014*

**Science**

You're welcome!
*October 2, 2014*

**Science**

It's adding if the forces are in the same direction. If you had 30 people on one side of the box and then 20 more joined them. You would have 50 people pushing in one direction. If you had 30 people on one side of the box and 20 on the opposite side then you would be the ...
*October 2, 2014*

**Science**

Imagine 15 people pushing a box in one direction and 10 people on the other side pushing against them. If you had 1 person each side pushing against each other would it move? What do you think the answer is?
*October 2, 2014*

**Science**

edit: my reply before was to your reply of 'B'? A nonzero force just means a force. It means that 0N isn't allowed as that wont affect anything. It's not D either I'm afraid. Damon said the correct answer there.
*October 2, 2014*

**Science**

Afraid not, try again. You can't have a force greater than the reaction force as Newtons 3rd Law states that 'Every action has an equal and opposite reaction'. Imagine kicking a wall. If you kick it gently your foot doesn't feel much of a force back but if you ...
*October 2, 2014*

**Science**

Imagine a football stationary on the ground or even moving through the air. You then apply a nonzero force (i.e. you kick it) What happens?
*October 2, 2014*

**physics**

Ignore the 2nd half of the question at first (the player 48.5m away). You need to find the range of the football. Work that out first. After that compare that distance to where the player is. i.e. find the distance between where the ball lands and 48.5m. Then remember that the...
*October 2, 2014*

**Physics wavelength question, help please .**

You're welcome :) Remember, the higher the frequency the higher the energy. That's why we have Blu Ray players and not Red Ray players.
*October 2, 2014*

**Physics wavelength question, help please .**

Use these E = hf Energy = Planck's Constant x frequency c = fλ Speed of light = freq of the light * wavelength of the light
*October 2, 2014*

**Math**

What do you think the answers are first?
*October 2, 2014*

**Vectors problem help?**

ahh ok. well, |A| = sqrt[ (3)^2 + (6)^2 + (-2)^2 ] -ve signs don't affect the length of the vector. That only tells you about the direction of it. |A| = sqrt[ 9 + 36 + 4 ] = sqrt [49] = 7 The length of the vector is 7. Unit vectors have length 1. So we need to divide A by ...
*October 2, 2014*

**Vectors problem help?**

Unit vector = V/|V| if V = ai + bj + ck |V| = sqrt(a^2 + b^2 + c^2) = length of the vector
*October 2, 2014*

**Physics**

Magnitude of a vector is its length: if v = ai + bj + ck |v| = sqrt(a^2 + b^2 + c^2) So that's the length. It's a scalar quantity. |b| = sqrt(16+4+4) = sqrt(24) |v| = |b| Parallel vectors: the dot product is 0. so. A.v = 0 or 2a + 3b - 1c = 0 The thing is there isn'...
*October 2, 2014*

**Math**

An interval is like a range. An interval could be from 3 to 8 for example which would be all the numbers between 3 and 8 inclusive. What is the context?
*October 2, 2014*

**Math--4 practice questions?**

What do you think the answers are first? I like to think of these as money. Imagine the first one there is you had €27 in your hand, something happened to it and now you have €21. So, what happened? Was money added or taken away? How much was added or taken away?
*October 2, 2014*

**physics**

edit: S = ut + (1/2)*a*t^2 Sorry about that. I was thinking of the upward throw and the - sneaked in.
*October 2, 2014*

**physics**

A motion question so think about the equations of motion: v = u + at v^2 = u^2 + 2aS S = ut - (1/2)*a*t^2 u = initial vel v = final vel t = time S = displacement a = acceleration which in this case is gravity so g = 9.8 m/s^2 Don't forget that when throwing up gravity is ...
*October 2, 2014*

**Math (Implicit Differention)**

ok let's see... x^(2/3) + y^(2/3) = 4 differentiating we get (2/3)*(x^(-1/3)) + (2/3)*(y^(-1/3)).dy/dx = 0 divide across by (2/3) to get x^(-1/3) + y^(-1/3).dy/dx = 0 Then replace the negative power with 1/ instead. e.g. x^-1 = 1/x 1/x^(1/3) + (1/y^(1/3)).dy/dx = 0 (1/y^(1...
*October 2, 2014*

**Math (Implicit Differention)**

Is is x^(2/3) or is it (x^2)/3 ? If it was the latter you could multiply both sides by 3 to get rid of any fractions straight away. Brittany, y' = -(2x/3) / (2y/3) = -x/y not y' = -(2x/3)-(2y/3)
*October 2, 2014*

**physics**

You need to use two equations: F = ma (force = mass*acceleration) and one of the equations of motion: S = ut + (1/2)*a*t^2 Where S = distance, u = initial vel, a = acceleration and t = time See if you can work it out now
*October 2, 2014*

**Physics**

I think you're missing the question part. In any case. You need to break up the force exerted by the teenagers into the horizontal and vertical components. The horizontal force is the only one that makes the sled move. you can make a right angled triangle if you draw it ...
*October 2, 2014*

**Chemistry**

Oh and I don't think this is a Chemistry question.
*August 17, 2009*

**Chemistry**

because The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. A day is how long the earth takes to rotate once and that in our time is 24 hours [well, ...
*August 17, 2009*

**math**

I think it was a typo: it should be = 3 - 2(7) -2(-4y) = 3 - 14 + 8y = 8y - 11
*August 16, 2009*

**Math/Algebra 2**

2/x + 3/4x = 8/4x + 3/4x = 11/4x
*August 16, 2009*

**alegbra**

x^2-15x-36=-72 therefore x^2-15x+36=0 when you solve this you get (x-12)*(x-3)=0 You can find the 2 solutions from that and multiply them. hope that helps
*June 29, 2009*

**Algebra 2**

sorry, i made a mistake 8(x) + 5(2x) = 360 8 per truck, 5 per car
*March 26, 2009*

**Algebra 2**

here is a hint, if trucks = x then cars = 2x then x + 2x = $360 see if you can get the rest now. just write what they told you in equation for. hope that helps
*March 26, 2009*

**math**

multiply the 1st equation by -2 and then add them to get rid of the y's [and hence find the x] once you have the value of x sub it into either of the two equations to find y. then just do x-y Hope that helps
*March 26, 2009*

**7th grade**

for the 1st post - to dim for the 2nd post - adequate hope that helps
*March 26, 2009*

**Algebra**

vol = l*w*h the question is that l is doubled to give 2l h is doubled to give 2h and w is tripled to give 3h. so the new vol = (2l)*(2h)*(3w) = 12*l*w*h so 'new vol' = 12*old vol Hope that helps
*March 23, 2009*

**Algebra**

yes, spot on. Well done
*March 22, 2009*

**Geometry**

A protractor maybe? Hope that helps
*March 22, 2009*

**Pre-Calculus**

well, from the above equation y = (x^2)/2 to get an equation of a line you need a slope and a point. You have a point and to get the slope we need to get dy/dx and sub in the value for x in the point given [in this example 4] Then sub your point (x1,y1) and the slope (m) into ...
*March 22, 2009*

**Algebra.**

almost, the < sign only changes to a > sign when both sides are multiplied by a minus. so the answer is x<1 Hope that helps
*March 22, 2009*

**Algebra**

Spot on. well done.
*March 22, 2009*

**4th grade**

1 US pint = 32 US tablespoons there is no work involved. It's a conversion. like 1760 yards in a mile or 1000Kg in a tonne
*March 22, 2009*

**Math**

I'll correct myself, yes you can I didn't think of the above method by Reiny. I never used that way before :) It's quite useful though. Sorry for my error
*March 22, 2009*

**Math**

No, you have to first use y - y1 = m(x - x1) [point slope form] and then rewrite in the form y = mx + c [slope intercept form] When you are given 2 points you have to find the slope first [m = (y2 - y1)/(x2 - x1)] then sub in the slope with either of the points in the equation...
*March 22, 2009*

**4th grade**

yes. All animals (and plants too - and stars aswell) are born [one way or another ] and eventually die. Which is the life cycle. hope that helps
*March 22, 2009*

**4th grade**

No, the moon orbits the earth and the earth orbits the sun but the moon does not orbit the sun. (rotate is not technically correct for this description of motion) Hope that helps
*March 22, 2009*

**Math**

yes it does. With (x1,y1) = (4,0) and m = 1 The equation for a line is y - y1 = m(x - x1) y - 0 = 1(x - 4) y = x - 4 So, yes you are right. Well done!
*March 22, 2009*

**Math**

First question: no, the zero can be dropped Second question: yes it can be changed into (y-2) = (4/5)*x and it can be also be re-written as y = (4/5)*x + 2 [slope intercept form] Hope that helps
*March 22, 2009*

**Calculus**

well to get a distance between points we use the distance formula but first we need the points themselves. Point 1 is found by subbing t=0 in for t in x(t) and y(t) Point 2 is found by subbing t=11 in for t in x(t) and y(t) I'll do point 1 x(t) = (0)^2 - 14(0) - 4 = -4 y(t...
*March 21, 2009*

**physics**

W = mg W = weight (in Newtons) m = mass (in Kg) g = acceleration due to gravity (in m/s^2) Force in also measured in Newtons so they just want W. Oh and g = 9.8 m/s^2 Hope that helps
*March 20, 2009*

**college**

You need to post the statements.
*March 20, 2009*

**Alegbra**

ok, you have a line x + 4y = 5 to find the slope re-write in the form y = mx + c where m is the slope and c is a constant in the above line m = -1/4. So we want the equation of a line parallel to the above line but goes through the point (7,9). As I said above parallel lines ...
*March 20, 2009*

**Alegbra**

Here is a clue for the question: Parallel lines have the same slope. You have 1 line - find its slope. Hope that helps
*March 20, 2009*

**math**

Trial and error really for x and y being whole numbers. You have to see, for example, how many 2's [the 2x bit] to take away from 4 [on the RHS] before it's divisible by -3 [from the 3y bit] For example, from -3y = 4 - 2x x = 5 will give -3y = 6 which means y = -2 The ...
*March 20, 2009*

**math**

There is a mistake in bobpursley's equations - both should have the same distance of 48. vs = velocity of stream vb = velocity of boat and Distance = Velocity*Time Downstream 48 = (vb + vs)*3 The stream velocity is +ve as the time is shorter downstream - the stream helps ...
*March 20, 2009*

**Math**

It's a straight forward pair of simultaneous equations. In this example just add the two equations to cancel out the y and find the x value. Once you have the x value sub it back into one of the equations to find y. Hope that helps
*March 17, 2009*

**math**

well, 49+72+108+121 = 350 and 350/35 = 10. That has got to be the oddest question I've ever seen :) Given the answer and have to find the question - odd :) Hope that helps
*March 17, 2009*

**math**

Firstly f(x)=(x=4)(x-2) is wrong you have two = signs. I'm assuming it's a + or another -. a) Well, you know f(x), so -f(x) just has a - in front of it. f(-x) means put -x in everywhere you see x b) f(x), -f(x) and f(-x) are all of the form y = ax^2+bx+c which is a ...
*March 17, 2009*

**Pre Calc**

Well if, 5! = 5*4*3*2*1 that's the same as 5*4! isn't it? or 5*4*3! ? Do you see now how to do the question? Hope that helps
*March 15, 2009*

**Pre Calc**

To me that doesn't seem like a complete question. You have 1 equation with 2 unknowns. You need a minimum of 2 equations to find 2 unknowns. Another way of looking at it is that the above equation is the equation for a circle with center (2,-3) and radius 3. So asking for ...
*March 15, 2009*

**Pre Calc**

Well, a geometric sequence is of the form; a, ar, a(r^2), a(r^3), ... , a(r^n) where t(0) = a, t(1) = ar etc. [the sequence 1, 1/2, 1/4, 1/8, 1/16,... is geometric with a = 1 and r = 1/2] Ok, hope that helps!
*March 15, 2009*

**Math**

Ok, I'll do the 1st one; first of all 8 - (-2/3) well, minus times minus = plus [e.g. -4*-4 = 16] so that becomes 8 + 2/3 Now we need to do the same with the rest of the equation to get 8 + 2/3 + 7 - 1 2/3 + 5 You how have to sort out 1 2/3 which is 1 and 2/3 which equals ...
*March 15, 2009*

**math**

I'd use a venn diagram. Simple, yet effective.
*March 15, 2009*

**physics**

I got r = 9.10x10^14 meters. A correction to the question above is ME = 5.98x10^24 Kg not 5.98x1024 Kg Maybe that's where the mistake is? Hope that helps!
*March 15, 2009*

**college math**

drwls, you made a slight mistake - you forgot a factor of 2 in the RHS of the equation. If N1 = x and N2 = 2x + 8 then the equation is x(2x+8) = 8 + 2*(2x + 8 + x) Which simplifies to x^2 - x - 12 = 0 which has two integer solutions. Hope that helps!
*March 14, 2009*

**Algebra II/ Trig**

I'd guess it's the area is what the question wants so we need only one of the angles. Now, CosA = 0.05 but A is not 152. [For one reason Cosine is -ve in the 2nd quadrant so the angle must in the 1st quadrant [0<A<90] Angle A = 87.1 Degrees So when you have the ...
*March 14, 2009*

**MATH**

Area of Trapezoid = h*((a+b)/2) where a and b are the two parallel sides and h is the perpendicular height. If your a and b are 12 and 5.4 and the perpendicular height is 6 then your equation above is correct.
*March 14, 2009*

**physics**

Yes. I believe so.
*March 14, 2009*

**physics**

yes -0.544 - (-3.40) = -0.544 + 3.40
*March 14, 2009*

**physics**

I'm fairly certain it's D i'll explain my reasons again - hope fully better :) Ok, my example is going to be UV radiation from the sun. a. it transfers energy to objects in the path of the electromagnetic waves When you are outside in the sun UV radiation is, for ...
*March 14, 2009*

**physics**

Force is C - Electromagnetic The Strong force binds gluons inside protons and neutrons Yes, I think D is right for the mechanical force one. Yes 5.1 I think it's D - All of the above Here is an example a - UV radiation causes sunburn b - UV radiation is used by Solar ...
*March 14, 2009*

**Algebra II**

Area of a triangle = (1/2)bcSinA Or in words, a half times the length of two sides times the Sin of the angle between those two lines. So Area = (0.5)*(20)*(12)*Sin(56) Area = 120*Sin(56) Area = 99.48 And rounded to the nearest 10th [or to one decimal place in other words] ...
*March 14, 2009*

**chemistry**

With Li, Na and K the reactions are exothermic [give out heat] and you would see flames and the metals would move vigorously on top of the water. The reactivity order is Li<Na<K so K is the most reactive. The reaction of an alkali metal with water gives a Hydroxide and ...
*March 14, 2009*

**math-calc**

I'm going to guess that the question is asking for the maximum and minimum of the cubic. Simply find f'[x] = 0 and you will find 2 values for x. To find which is the max and min find f''[x]. and put in the two different values you got [say x1 and x2] and if f&#...
*March 13, 2009*

**math-calc**

I made a slight error. i dont want f'[0], i want f'[x] = 0 to find x = something. so we get 5e^(2x) + 2e^(2x)(-4+5x) = 0 divide across by e^(2x) we get 5 + 2(-4+5x) = 0 5 - 8 + 10x =0 10x = 3 x = 3/10 Sorry about the mistake in my first post. hope that helps
*March 13, 2009*

**math-calc**

Differentiate and put equal to zero. f'[x] = 5e^(2x) + 2e^(2x)(-4+5x) f'[0] = -3 So the x-coordinate is -3 I'd guess that that is what the question wants. Hope that helps
*March 13, 2009*

**math-calc**

f(x) = inf when 6x+3 = 0 or when x=-1/2 That is one of the asymptotes which separate the graph. as for increasing and decreasing, well, from -inf going to -1/2 as x increases y decreases and from -1/2 to inf as x increases y decreases also. If you draw it it has the shape of y...
*March 13, 2009*

**math-calc**

it's turning points are when [1] x*7 = 0 or x = 0 [2] (x+2)^2 = 0 or x - -2 The graph is increasing when (-12 to -2) and (0 to 10) To work this out find the turning points by finding f'[x]=0 ok hope that helps
*March 13, 2009*

**calculus**

f[x] = 9x + 3/x f'[x] = 9 - 3/(x^2) f'[x] = 0 at min/max 9 - 3/(x^2) = 0 multiply across by x^2 to get 9x^2 - 3 = 0 x^2 = 1/3 x = 1/sqrt(3) or x = -1/sqrt(3) which i will call x1 and x2. to find which is the min and which is the max get f''[x] and sub in the ...
*March 13, 2009*

**Science**

Overall it's a mixture. Like table salt is a mixture [NaCl and KCl] it's the components of the mixture that are compounds but not the overall contents. If you put peas and beans in a bowl that's a mixture but peas and beans are made up of lots of different chemical...
*March 13, 2009*

**Algebra**

x = number of houses with floor plan 1 y = number of houses with floor plan 2 x(175,000) + y(200,000) = 7,200,000 7,200,000 is the value of the 38 houses made up of a number of plan 1 houses (x) and a number of plan 2 houses (y). Then solve simultaneously to find x and y. ...
*March 13, 2009*

**It's been more than 24 hours and no answer...**

Well, the y-value doesn't change and the x-value decreases by 5. If, for example, we had the point (7,4) Under the above translation becomes (2,4) Hope that helps
*March 13, 2009*

**Maths**

if it's 1/(2x^2) - x + 4 = 0 Multiply across by 2x^2 to get 1 - 2x^3 + 8x^2 = 0 2x^3 - 8x^2 - 1 = 0 Which is a nasty enough cubic with only 1 root. If the question is (1/2)x^2 - x + 4 = 0 use the -b formula which gives 2 complex roots: 1 + sqrt(7)i and 1 - sqrt(7)i. Hope ...
*March 13, 2009*

**algebra 2**

you can factor x^2 - 2x - 8 = 0 (x-4)(x+2)=0 therefore the three zeros [or 'roots' as I know them as] are x = 4, -1, -2
*March 13, 2009*

**physics**

I think it's A also. Increase Charge = Increase EFS Increase Distance = Decrease EFS
*March 12, 2009*

**chemistry**

Ah, I should have the same as the original figure - 2 decimal places. Thanks!
*March 12, 2009*

**chemistry**

c = f*l c = speed of light f = frequency l = wavelength c = 3x10^8 m/s [a constant] l = c/f l = 3x10^8/6.67x10^14 l = 4.49775x10^-7 l = 449.8 nm Hope that helps
*March 12, 2009*

**chemistry**

1 mol Potassium = 39g [Atomic Mass of K] x mol Potassium = 25g x = 25*1/39 = 0.641 mol Hope that helps.
*March 12, 2009*

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