Wednesday

February 10, 2016
Total # Posts: 37,530

**maths**

well, 6000 is 5/12 std above the mean. Look that up in your Z table. You can play around with this stuff at http://davidmlane.com/hyperstat/z_table.html
*December 31, 2015*

**Math**

you want to solve for t in 400t - 16t^2 = 2400 Then find the difference in the two times.
*December 31, 2015*

**probability**

well, using brute force, just list the ways you could pair up the socks. How many of those ways fit the requirements?
*December 30, 2015*

**Physics**

for inital velocity v, we have h(t) = vt-(g/2)t^2 This reaches a max height at t=v/g, and h(v/g) = v(v/g) - (g/2)(v/g)^2 = v^2/g - v^2/2g = v^2/2g So, we see that max height is directly proportional to v^2 So, double v, and you quadruple the max height. M does not matter, as ...
*December 30, 2015*

**Math**

In the first G.P. the numbers are a, ar, ar^2 To form the A.P., the differences are constant, so ar-a = ar^2-4 - ar Then, forming a new G.P. with constant ratio, we have (ar-1)/a = (ar^2-4-1)/(ar-1) Solving for a and r, we have a=1, r=3 or a = 1/9, r=7 The 1st G.P. is 1, 3, 9 ...
*December 30, 2015*

**physics(optics)**

nothing.
*December 30, 2015*

**Physics**

well, the acceleration is 4 m/s^2, and F=ma.
*December 30, 2015*

**Math advanced function**

Since a quadratic can two solutions, and a trig function can two solutions per period, I expect that 4 solutions is as many as you can have. For example, sin^2(x) = 1/4 has 4 solutions in one period. sin^2(x) = 2 has none, sin^2(x) = 1 has two Maybe you can find some with an ...
*December 30, 2015*

**Math**

Draw the triangles. Recall that the sides are in the ratio 1:√3:2 Label the longest hypotenuse, and then work down to get the desired leg's size. I get 6. I am assuming there are only two triangles.
*December 29, 2015*

**Physics**

check your previous post.
*December 29, 2015*

**maths**

In that case, recall that one log is the reciprocal of the other. So, If you let u = log3x, then you have u + 1/u = 5/2 2u^2 - 5u + 2 = 0 (2u-1)(u-2) = 0 u = 1/2 or u=2 Thus, u = √3 or 9
*December 29, 2015*

**maths**

Or, did you mean log3x+logx3 = 2.5 ?
*December 29, 2015*

**math**

If the lawn has side x meters, then lawn area: x^2 total area: (x+1)^2 path area: (x+1)^2-x^2 = 2x+1 So, we have x^2 = 2x+1 + 23 Now just find x.
*December 29, 2015*

**Physics**

original: <0,-398> wind: <-104,0> result: <-104,-398> = 411 at 195° or 411 at S15°W To get back on course, you just need to negate the wind. So, you want <x,y> + <-104,0> = <0,-398> <x,y> = <104,-398> or 411 at S15°E
*December 29, 2015*

**stats**

9 dancers total 5 warmed and had no injuries (W & ~I) You want ~W or I = ~(W & ~I) So, your probability is 1 - 5/9 = 4/9
*December 29, 2015*

**maths**

well, 3000 is 20 times 150, so it will take 20 times as long, right?
*December 29, 2015*

**Maths**

which two factors of 15 differ by 2?
*December 29, 2015*

**Factorize**

a^3-b^3 = (a-b)(a^2+ab+b^2) so, x^3 - (x+y)^3 = (x-(x+y))(x^2+x(x+y)+(x+y)^2) Now just simplify that.
*December 29, 2015*

**Maths**

well, just substitute: √(1-x^2) = √(1-sin^2 θ) Now, what is your most basic trig identity?
*December 29, 2015*

**chemistry**

same as 1 mole of any compound: Avogadro's Number of molecules. Maybe you should review molar mass...
*December 29, 2015*

**Wave**

look at the units: f = 1/s speed = m/s So, wavelength (m) = speed/f
*December 29, 2015*

**Math**

w+d = 46 (w+4)/(d+4) = 7/2 Now just solve for w and d.
*December 29, 2015*

**St. Francis English medium school.**

If the price is each, then we have cost: 110 revenue: 110, with one left over On the other hand, he made a gain of 10% one each clip sold.
*December 28, 2015*

**algebra**

If the length is y, then the width w is 1 + y/4. So, 2(1 + y/4 + y) = 62 Now just solve for y, and you can find w.
*December 28, 2015*

**Math**

If you mean (2x+7)/(2x^4+21x^3+35x^2-37x+46) then that is approximately (2x+7)/((x+7.966203)(x+3.527066)(2x^2-1.98654x+1.63717)) Now you can just use partial fractions on that mess.
*December 28, 2015*

**mathematics**

And assuming the usual sloppiness in the numerator, we have (x²+x+4)/[(1-x)(x²+1)] = (2x+1)/(x²+1) + 3/(1-x) amazing how little difference it made, eh?
*December 28, 2015*

**maths**

for x in [0,10000), f(x) = 900 for x in [10000,15000), f(x) = 900+.02(x-10000) for x in [15000,25000] f(x) = 900+.02(x-10000) + 500 I think you can discuss the continuity. If not, draw the graph and it will become clear.
*December 28, 2015*

**mathematics**

this cannot be more straightforward, if you have read the relevant section in your text. Namely, the equation for a circle with center at (h,k) and radius r is (x-h)^2 + (y-k)^2 = r^2 Surely you can now see what to do...
*December 28, 2015*

**<b>͡° ͜ʖ ͡°</b>**

:-)
*December 28, 2015*

**pi -- NOT pie!**

grrr
*December 28, 2015*

**PHYSICS**

Resolve F1 and F2 into x- and y-components, and then just add them up.
*December 28, 2015*

**physics**

conserve momentum: 5(-10) + 6(12) = (5+6)v That will give the final velocity v. Then find KE (1/2 mv^2) for each body before and after the collision.
*December 27, 2015*

**physics**

since C=2πr, just multiply the circumference by the revs/min. That will give the speed in cm/min.
*December 27, 2015*

**Math**

I suggest that would be 3/5 * 3 = 9/5 mi
*December 27, 2015*

**Calculus**

Of course it works. Why don't you show your work and the reason why you rejected it? 2/((2-x)(x+2)^2) = (1/8) (1/(x+2) + 4/(x+2)^2 - 1/(x-2)) So, the integral is just (1/8) (ln(x+2) - 4/(x+2) - ln(x-2)) = (1/8) (ln((x+2)/(x-2)) - 4/(x+2)) + C
*December 27, 2015*

**math**

for 2 cm, r=2. So, just figure the circumference of the circle of radius 2... 100/3 rev/min * 2π*2 cm/rev = 400π/3 cm/min similarly for r=15.
*December 27, 2015*

**komenco**

Assuming you mean Geometric Sequence, we have For The AP, a=7, so we want d. The ratio between terms of a GP is constant, so we form the ratio between successive given terms of the AP: (7+d)/7 = (7+4d)/(7+d) d=14 or d=0 Now, d=0 is not very interesting: AP = 7,7,7,7,7... GP...
*December 27, 2015*

**mustapha**

well, first evaluate 10^(1/3) = 2.1544 Then just multiply as usual.
*December 27, 2015*

**Math**

the derivative of sec(u) is sec(u) tan(u) But, if u is a function of x, then we have to apply the chain rule. Since u=tanx, then du/dx = sec^2(x) So, the final damage is sec(tanx) tan(tanx) sec^2(x)
*December 27, 2015*

**math**

well, what is half the circumference of the circle? Then just multiply that by the cost per foot.
*December 27, 2015*

**Math**

I think you've both gone stray. See http://www.wolframalpha.com/input/?i=derivative+%28sinx%2F%281%2Bcosx%29%29 and http://www.wolframalpha.com/input/?i=derivative+%28sinx%2F%281%2Bcosx%29%29^2
*December 27, 2015*

**math**

Because y(0) = 0. It helps if you actually read what I write. Or maybe it has something to do with the mysterious "a".
*December 27, 2015*

**math**

well, f'(x) = cos(√2 x) - √2 x sin(√2 x) Not sure what a has to do with things, but if you meant x=0, then f(0) = 0 f'(0) = 1 So, you want the line with slope 1, which passes through (0,0). No too much of a challenge there, eh?
*December 27, 2015*

**math**

cancel what out? There are no common factors.
*December 27, 2015*

**math**

well, the 1st three terms are 2^2, 3^3, 4^4, so what's your best guess?
*December 26, 2015*

**physics**

As I recall, the force grows as the ratio of the areas of the pistons. That means, as the square of the diameter. So, since 6 = 3*2, the force would be 3^2 * 20 Review your text on this subject. I'm sure there are examples. And you can always rely on google for lots of ...
*December 26, 2015*

**Calculus**

rearranging things a bit, we have y' = y(t+1) + t+1 y' = (y+1)(t+1) dy/(y+1) = (t+1)/t^2 dt ln(y+1) = ln(t) - 1/t + c y+1 = t e^(-c/t) + c2 or, altering the c values, y = ct e^(-1/t) + c2 y(1) = 0, so 0 = c/e + c2, so c2 = -c/e y = c(t e^(-1/t) - 1) We can ignore the c...
*December 25, 2015*

**Math**

how about if we start by saying y-1 = 3sin((1/2)(x+pi)) and y+2 = -1/3 cos(2(x - pi/2)) the shifts and scalings should now be clearer.
*December 25, 2015*

**math**

There are infinitely many chords passing through any point within the circle. Two such chords, easy to describe are x=2 and y=3.
*December 25, 2015*

**Statistics**

18 rings total, so that would make the probability 10/18 * 9/17
*December 25, 2015*

**math**

There are infinitely many chords passing through any point within the circle. Two such chords, easy to describe are x=2 and y=3. ---------------------------------------- Clearly, the vertex of the triangle is at (0,5), so the altitude is 3. The base of the triangle goes ...
*December 25, 2015*

**math**

Draw diagonal BD Then triangles ABD and CBD are isosceles. Hence, their altitudes bisect their bases and their vertex angles.
*December 25, 2015*

**physics**

54.45 mph = 79.86 ft/s If the rock was thrown with an initial speed k, then k-32*2.75 = -79.6 k = 8.4 ft/s So, the rock was thrown upward at 8.4 ft/s from a height h: h - 32*2.75 - 16*2.75^2 = 0 h = 209 ft
*December 25, 2015*

**mathematics**

(x-1)(x-2)(x-k) = x^3 - (k+3)x^2 + (3k+2)x - 2k k+3 = p 3k+2 = 2 q = -2k Looks like k=0, so p=3 q=0 and we have x(x-1)(x-2) = x^3 - 3x^2 + 2x
*December 25, 2015*

**maths**

or, using partial fractions, 2 - (5/9)/(x+2) - (13/9)/(x-1) + (1/3)/(x-1)^2
*December 25, 2015*

**Trigonometry- ??????**

oh come on. If ab=0, then either a=0 or b=0 So, we have tanx = 0 --> x is a multiple of pi or sin^2(x) = 2 --> no solutions there.
*December 24, 2015*

**Trigonometry- ??????**

tan(x) sin^2(x)=2tan(x) tanx(sin^2(x)-2) = 0 How about now?
*December 24, 2015*

**Algebra 1**

39.80x + 49.70y <= 150,000
*December 24, 2015*

**Math**

looks good to me. or, you could have noted the 41-22 = 19%, and that would be 76.
*December 24, 2015*

**math**

the units would be dollars/yd^2 The rate of change is always ∆y/∆x, so the associated units just follow along. y might be the cost (dollars) of some quantity x (yd^2) of carpet.
*December 24, 2015*

**Calculus**

u = sinx du = cosx dx so, dx = du/cosx = du/√(1-u^2) sinx(cosx)^2 dx = u(1-u^2)/√(1-u^2) du = u/√(1-u^2) du Now, let v = √(1-u^2) dv = -u/√(1-u^2) du and you have -v dv integrate that to get -1/2 v^2 = -1/2(1-u^2) = -1/2 (1-sin^2(x)) = -1/2 cos^2(...
*December 23, 2015*

**Calculus**

because now we are using u, not x. If, after integration on u, you substitute back into terms of x, then you would use the limits [0,2]. When x=0, u=3 and when x=2, u=5.
*December 23, 2015*

**Calculus**

∫[0,2] x√(5-√(4-x^2)) dx Let u = 5-√(4-x^2) du = x/√(4-x^2) dx so, x dx = (5-u) du and you now have ∫[3,5] √u (5-u) du and I'm sure you can handle that, eh?
*December 23, 2015*

**Math**

n is starting population. t is time period k indicates how fast it grows. To use it, um, just plug in your numbers... Surely, knowing the formula, you have examples of its use. If not, google is your friend.
*December 23, 2015*

**Algebra 2**

you have the sum of two cubes, so it factors into (3x+5)((3x)^2-(3x)(5)+5^2) = (3x+5)(9x^2-15x+25) It's easy to check that the quadratic has no real solutions. Just use the quadratic formula, learned long ago in Algebra I...
*December 23, 2015*

**MATH Please help!**

if the dimensions increase by a factor of 3, the area increases by a factor of 3^2, so A is correct. 13^2 * 3^2 = (13*3)^2 = 39^2
*December 23, 2015*

**math**

domain is positive integers range is (0,N] where N is the maximum time for a single painter. Further restrictions depending on the maximum number of painters, and other information on their required times.
*December 22, 2015*

**math**

clearly, the mass depends on the number of candies, which is an easily controlled integer value.
*December 22, 2015*

**Gwu**

I think that is supposed to read and spends it takes .75mi * 1hr/2mi = .375hr = 22.5 min to travel between stops. So, assuming we start counting as the train arrives at the 1st intersection, it takes (in minutes) 12*.75 + 11*22.5 = 256.5 minutes before it leaves the final ...
*December 22, 2015*

**SCIENCE**

surely it would have taken less time just to look in your text, or google, rather than post here and wait.
*December 22, 2015*

**Algebra**

Note that y increases by 4 when x increases by 1. So, the slope is 4. That should help.
*December 22, 2015*

**metreology**

just review the wavelengths for the parts of the spectrum.
*December 22, 2015*

**chemistry**

google is your friend. Try it. Many discussions.
*December 22, 2015*

**Happy Christmas and Merry New Year!!**

Happy RamaHannaKwanzMas!
*December 22, 2015*

**Algebra 2**

Since tan(x) has a midline of y=0, and this is shifted down 4 units (due to the -4 at the end), so is the midline: y = -4
*December 22, 2015*

**maths, physics,**

Maybe if you show your work, you can learn where you went wrong.
*December 22, 2015*

**maths, physics,**

unless otherwise denoted, such as S20°E, headings are indeed clockwise from north. So, the plane (apparently aka helicopter)'s velocity is 400<0.939,0.342> and the wind is 70<-0.707,0.707> <326.11,186.29> = 375.568 at 60.3°
*December 22, 2015*

**Science**

this is just the usual 30-60-90 right triangle, with hypotenuse 100. Now just find the sides.
*December 22, 2015*

**victoria university college,Myanmar,mechanical pri**

No idea. How many kW does the machine use? Then just multiply by 7 to get kW used and then multiply by $.08 to get cost
*December 22, 2015*

**math**

what a deal! Oh - was there a question in there somewhere?
*December 21, 2015*

**statistics**

This just like drawing without replacement, so your probability is 8/25 * 7/24 = 7/75
*December 21, 2015*

**pharmacy tech**

or just use the 5% solution and add water. Since 3% is 3/5 of 5%, just use 3/5 of the 30mL and fill the rest with water: 18 mL 5% + 12 mL water Or, for a much slower method, pour some 1% solution in a beaker and let it evaporate. Since 1% is 1/3 as much as 3%, start out with 3...
*December 21, 2015*

**geomtery**

You know the three angles sum to 180, so 3x+9 + 8x+11 + 5x-8 = 180 16x + 12 = 180 ... Now you can find x, and thus the three angles.
*December 21, 2015*

**Algebra**

since the coefficients of x and y are the same, yes they are parallel.
*December 21, 2015*

**statistics**

you can play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
*December 21, 2015*

**math**

since time = distance/speed, time out = d/5 time back: d/3 avg speed = total distance / total time = 2d/(d/5 + d/3) = 2/(1/5 + 1/3) = 2/(8/15) = 15/4 Close to 4, but not quite.
*December 21, 2015*

**maths**

4/3 π r^3 = 1/3 π r^2h 4r = h ...
*December 21, 2015*

**maths**

the ratios are πr^2h : π/3 r^2h : 2π/3 r^3 = πr^3 : π/3 r^^3 : 2π/3 r^3 I expect you can take it from there. Just factor out the common values and clear the fractions as needed.
*December 21, 2015*

**maths**

If the three roots are r,s,t then their product rst = c/a. So, if r = -1, then st = = c/r = c/-1 = -c.
*December 21, 2015*

**math**

I have an idea. Why don't you give it a try. To start with, 2 is a factor of any even number...
*December 21, 2015*

**math**

I hope -4x-31 is one of the choices. That would be easiest. Of course, there are many many other equivalent expressions...
*December 21, 2015*

**maths**

any number whose digits sum to a multiple of 9, is divisible by 9. So, ...
*December 21, 2015*

**our own English school**

By an even multiple of 2, do you mean a multiple of 4? As in 6 is an odd (3) multiple of 2, but 24 is an even (12) multiple of 2? In any case, just pick any multiple of 2 or 4, as required, whose digits sum to 9. Such as 72, 234, 69732, etc. Read about "casting out nines&...
*December 21, 2015*

**Math**

by now surely you know that |<a,b>| = √(a^2+b^2)
*December 21, 2015*

**Algebra**

Eh? I've never seen an or written like that... It's always been in two parts: x < -5 OR x > +5
*December 21, 2015*

**mathamatic**

Some of these are simple arithmetic or geometric sequences. Other are easily recognizable powers, such as n^2 or 2^n, or are Fibonacci-like. Why not take a shot at them and let us know what you come up with?
*December 21, 2015*

**mathematics**

No idea. You have a mish-mash of notations. Try using the most common online one: ^ for power, as in 12araisedto Power3b = (12a)^(3b) and so on for your others.
*December 21, 2015*

**mathematics**

If the son is x, the father is 5x. So, x + 5x = 78 ...
*December 21, 2015*

**vectors**

well, you know that you need 2^2+1^2+x^2 = 1 good luck with that, since x^2 is always positive. I suspect there is more to this problem than you posted.
*December 21, 2015*