Sunday

February 26, 2017
Total # Posts: 29,414

**Math**

A = x*y 32 = x+2y x = 32-2y A = (32-2y)y = 32y-2y^2 or y^2-16y = -A/2 you did not say if you are in algebra or calculus so I will do it the algebra way by completing the square y^2 -16y + (16/2)^2 = -A/2 + 64 (y-8)^2 = -(1/2)(A-128) y = 8 x = 16 and the area is 128 ft^2

*January 9, 2017*

**please show your attempts**

We are teachers. We do not do tessts for people.

*January 9, 2017*

**physics**

+250 :) weight = m g = 55*9.8 = 539 Newtons That is the normal force on the floor Max friction = .56*539 = 302 N

*January 8, 2017*

**physics**

weight = w = m g normal force = m g cos theta ratio = cos theta so cos 17 and cos 30

*January 8, 2017*

**calculus**

Oh, intercepts y = x^3-6x^2 0 = x^2 (x-6) bounced off x axis at x = 0 crossed x axis at x = 6

*January 8, 2017*

**calculus**

slope = 3 x^2 -12 x =3 x (x-4) second derivative (curvature) = 6 x - 12 so the slope is 0 at x = 0 and at x = 4 at x = 0 is that a min or a max or in inflection point? second derivative = -12 That is a maximum, starts down from there at x = 4 is that a min or a max or an ...

*January 8, 2017*

**Chemistry**

CuCO3 = 64+12+48 g/mol = 124 g 31/124 = .25 mol CO2 = 12+32 = 44 g/mol so 11 g for .25 mol for CuO, subtract:) 31-11 = 20 grams check: CuO = 64+16 = 80 g/mol .25*80 = 20 grams sure enough

*January 8, 2017*

**calculus**

two negative numbers can not add to +1

*January 8, 2017*

**calculus**

b.f(x)=x^3=x-4 Typo, makes no sense c. f(2)=8 f(-1)=-1 so 9/3 average slope =3 f' =3x^2 3 x^2 =3 x= sqrt(1) which is 1 !!!! but also -1 d f(4) = 2 f(0) = 0 so slope = 2/4 = 1/2 f' = (1/2)x^-1/2 = 1/2 x = 1 again

*January 8, 2017*

**Math**

a + b + c = 975 a - x = 12 b - x = 345 c - x = 126 --------------add a+b+c -3 x = 483 so 975 - 3 x = 483 3 x = 492 x = 164

*January 8, 2017*

**physics**

mapple Vapple +mweath*0 = (mapple+mearth) V V = Vapple (mapple)/(mapple+mearth) so yes mapple/(mapple+mearth) is not very big it might be kind of hard to measure :)

*January 8, 2017*

**physics**

The earth moves under your feet (but just a little).

*January 8, 2017*

**Math**

L(1-cosT) = 1/3 foot sin T = 4 feet/L so L sin T =4 1-cosT = 1/3L L sinT = 4 cosT = (3L-1)/3L so cos^2T = (9L^2 -6L+1)/9L^2 so 1-cos^2T = (6L-1)/9L^2 which is sin^2 T but sin^2T =16/L^2 so 16/L^2 = (6L-1)/9L^2 144 = 6L-1 6L = 145 L = 24.2 feet check my arithmetic!

*January 8, 2017*

**calculus**

dV = surface area * dr so dr/dt = dV/dt/(4 pi r^2) dr/dt = 2 /(4 pi *64)

*January 8, 2017*

**math**

well, you just said math, not calculus, which is why I completed the square to find the vertex of the parabola in the other problem. 3 4 5 triangle x = 4 y = 3 hypotenuse = 5 dy/dt = -2 ============================= x^2 + y^2 = 25 2 x dx/dt + 2 y dy/dt = 0 dx/dy = -(y/x)dy/dt...

*January 8, 2017*

**math**

r = x (1000-2x) r = 1000 x -2 x^2 2 x^2 -1000 x = -r x^2 - 500 x = -(1/2)r x^2 -500 x + 250^2 = -(1/2)r + 250^2 (x-250)^2 = -(1/2)(r-2(250)^2 ) x = 250 r = 2*250^2 = 125,000

*January 8, 2017*

**Algebra**

[ (x/3) -5 ] 7 = 28 (x/3) -5 = 4 x/3 = 9 x = 27

*January 8, 2017*

**calculus**

check end points f(-2) = -2+8 = 6 f(2) = 2-8 = -6 now find where derivative is zero f' = 1 -3x^2 = 0 when x = 1/sqrt3 or x = -1/sqrt3 if x = 1/sqrt 3 f = 1/sqrt3 -1/3sqrt3 =(2/3sqrt3) if x = -1/sqrt3 f = -1/sqrt3 +1/3sqrt 3 = -(2/3sqrt3) so the max and min are at the end ...

*January 8, 2017*

**calculus**

Well, try one of them. function is continuous and differentiable from 1 to 3 (note not at zero) f(3) = 3-1/3 = 8/3 f(1) = 0 [f(3)-f(1)]/(3-1) = 4/3 so where is the derivative 4/3? f'(x) = 1 + 1/x^2 where does 1+1/x^2 = 4/3 ? 1/x^2 = 1/3 x = sqrt 3 yes, that is between x = ...

*January 8, 2017*

**Physics**

pm=1.6gcm^-3 nonsense V = 40 cm^3 so mass = 20 + 40 * density of Hg which is not 1.6 g/cm^3

*January 8, 2017*

**Math**

original = p cents / pizza 10 p = total cost 9(p+60) = same total cost so 10 p = 9(p+60) p =540 cents = 5.40 per pizza so $54

*January 7, 2017*

**math**

n = original 1.2 n = before 300 .2 * 1.2 n = 300 so 1.2 n = 1500 n = 1250 books originally ===================== check ===================== 1.2 * 1250 = 1500 +300 = 1800 1.2*1.2*1250 = 1800 sure enough

*January 7, 2017*

**Algebra 1**

x = [2p+/-sqrt(4p^2+32p^2) ]2 = [2 p + sqrt(36 p^2) ]/2 = [2 p + 6 p ]/2 = 4 p

*January 7, 2017*

**Math**

(43/2)(3/4)= 129/8 left after tacos (2/3)(129/8) used for burgers times 4 for number of 1/4 lb burgers 4(2/3)(129/8) = 129/3 = 43 burgers

*January 7, 2017*

**another subtraction error**

360 - 12 = 348 348 = 23 t -23t/2 696 = 23 t t = 30.3 a = 23/30.3 = .759 m/s^2

*January 7, 2017*

**Physics**

freight train goes 6 t our train goes 6t+360 Vi = 29 Vf = 6 a assumed negative v = Vi - a t 6 = 29 - a t a t = 23 d = 6t+360 = 29t-(1/2)a t^2 360 = 23 t -(1/2)(23 t) 720 = 23 t t = 31.3 seconds to crash a = .74 whoops, forgot the .4 seconds to react we go 14.5 m he goes 2.4 m ...

*January 7, 2017*

**Algebra 1**

You are welcome.

*January 7, 2017*

**Algebra 1**

n + n+1 + n+2 + n+3 + n+4 = 5 n + 10 so (5n+10)/5 = 13 5n+10 = 65 5 n = 55 n = 11 so 11 , 12, 13 , 14, 15 old sum was 65 new sum is 53 difference is 12 so 12

*January 7, 2017*

**Physics**

Not really. I bet you have heard the word "Impulse" that is force * time which is change of momentum F = m a = m dv/dt so F dt = m dv = "impulse" but m dv is change in m v and m v is "momentum therefore F * time = change in momentum = impulse

*January 7, 2017*

**Physics**

change in momentum = force * time force up = 800 -55(9.81) = 260 N net up force so momentum = m Vi = 260*.25 = 65 so Vi = 65/55 = 1.18 m/s up (1/2)mVi^2 = m g h h = Vi^2/[2(9.81)] = .071 meters = 7.1 cm

*January 7, 2017*

**algebra**

x^2 - 3 x = 4 x^2 -3 x +(3/2)^2 = 4 + 9/4 (x-1.5)^2 = (1/4)(16 + 9) (x-1.5)^2 = (1/4)(25) = 25/4 x-3/2 = +/- 5/2 x = 3/2 +/- 5/2 x = 4 or x = -1

*January 7, 2017*

**Algebra 2**

You are welcome.

*January 7, 2017*

**Algebra 2**

w = x L = (x+1) H = (x-4) w L H = 84 so x(x+1)(x-4) = 84 but the easy way is to look at the answers listed 7 is one bigger than 6 4 is one bigger than 3 so it must be one of the last two if x = W = 6 L=7 H=6-4 = 2 that works if x =W= 4 L = 5 etc, does not work so 2,6,7 works (...

*January 7, 2017*

**Physics**

Fe 7.87 g/cm^3 Ag 10.5 g/cm^3 Viron* 7.87 + Vag*10.5 = 30 Viron + Vag = 20.4 ok?

*January 7, 2017*

**Physicsthe weight on e**

Our spring scales would not work on the moon correctly. We would have to multiply the measurement in grams or kilograms by 6 to get the right answer :) On the other hand a balance scale would work fine.

*January 7, 2017*

**Physics**

This is the second question in a row which confused mass and weight or force. Are you using the same old physics book I wonder?

*January 7, 2017*

**Physics**

well, 250*0.85 = 212.5 cm^3 so it displaces 212.5 grams of water assuming water has density of 1 gram/cm^3 If your book does force in grams, that is the answer. However that 212.5 grams is really the MASS of water displaced. To get the force up you really should multiply that ...

*January 7, 2017*

**Physics**

by the way, what we worked with here was mass, not weight. If this is a Physics course, your book should do mass in kg and weight in Newtons or mass in g and weight in dynes. weight = mass * acceleration of gravity. mass is the same on another planet, weight is different.

*January 7, 2017*

**Physics**

holds 40 g water that is volume = 40 cm^3 since density of water is about 1 g/cm^3 mass = 20 + 40*density of Hg density of Hg = 13.5 g/cm^3 so mass = 20 + 40*13.5 grams

*January 7, 2017*

**Algebra 1**

You are welcome.

*January 7, 2017*

**Algebra 1**

a = b + 2 c b = 2 c so a = 2 c + 2c = 4 c a + b + c = 77 4 c + 2 c + c = 77 7 c = 77 c = 11

*January 7, 2017*

**math**

you could do this by dividing the areas but that is not safe because it might not be exact one way or the other so 6 * 1.5 = 9 8 * 1.5 = 12 6*8 = 48 exactly

*January 7, 2017*

**Math**

4b+2p = 34 p = b-4 4 b + 2(b-4) = 34 4 b + 2 b - 8 = 34 6 b = 42 b = 7

*January 7, 2017*

**algebra**

3 z^2 = -108 z^2 = -36 z = +/-6 sqrt -1 = +/- 6i

*January 7, 2017*

**algebra**

5 x^2 = 651-536 = 115 x^2 = 23 x = +/- sqrt 23 = +/- 4.80

*January 7, 2017*

**Math**

49 - 2v

*January 7, 2017*

**Math**

three choices for the first digit 2 choices for the second 1 choice for the third 3*2*1 = 6 1 2 3 1 3 2 2 1 3 2 3 1 3 1 2 3 2 1

*January 7, 2017*

**algebra**

54 = 2*27 = 2*3*3*3 6 and 9 is 15 so (w-6)(w-9)

*January 7, 2017*

**Calculus**

5[xdy + ydx ] +x^2 dy+y(2x dx)=0 dy(5x +x^2) + dx(5y+2xy) = 0 dy/dx = =(5y+2xy)/(x^2+5x)

*January 6, 2017*

**Chemistry**

Ph determination

*January 6, 2017*

**Chem 111**

1000 kg/m^3 V = pi (d^2/4)h d = 6 ft = 1.83 m h = 17.5 ft = 5.33 m so V = [pi(1.83^2)/4 ]5.33 m^3 mass= 1000 * V in kg there are about 2.2 pounds/kg

*January 6, 2017*

**Math**

(2*27 + n)/3 = 29 54 + n = 87 n = 33

*January 6, 2017*

**Need help with vector questions posted below**

+1 1 3 -1 2 n +2 m 1 determinant = 0 2 + 2n -3m -12 -nm +1 = 0 2n-9 -m(3+n) = 0 m = (2n-9)/(3+n)

*January 6, 2017*

**maths**

everything in thousands two points on line (4,22) and (6,30) (30-22)/(6-4) = slope so slope = m = 4 c = 4 n + b 22 = 16 + b b = 6 so c = 4 n + 6 if n = 4.5 c = 4(4.5) + 6 c = 18+6 c = 24 so 24,000

*January 6, 2017*

**Vectors - Maths [Second Question]**

+1 -1 +2 +1 +2 -4 +m +6 -12 det = 0 -24 +12 +4m -4m +24 -12 = 0 I get any old m

*January 5, 2017*

**Vectors - Maths**

+1 1 3 -1 2 n +2 m 1 determinant = 0 2 + 2n -3m -12 -nm +1 = 0 2n-9 -m(3+n) = 0 m = (2n-9)/(3+n)

*January 5, 2017*

**calculus**

f(x+h) = 1/(2x+2h) f(x) = 1/2x f(x+h)-f(x) = (2x -2x-2h)/2x(2x+2h) = -2h/(4x^2+4xh) divide by h = -2/(4x^2+ 4xh) let h--->0 = -2/4x^2 = -1/2x^2

*January 5, 2017*

**Calculus**

Oh well h = 9 cm r = (6/12)9 = 4.5 cm dV = pi r^2 dh so dV/dt = pi r^2 dh/dt -3 cm^3/min = pi (4.5)^2 dh/dt so dh/dt = -3/[ pi(4.5)^2] about .047 cm/min

*January 5, 2017*

**Calculus**

No. The answer is in cm/min not cm^4/min. I did not check the arithmetic.

*January 5, 2017*

**Calculus**

I and also Steve have answered a million of these. For example: http://www.jiskha.com/display.cgi?id=1415757944

*January 5, 2017*

**incomplete**

earned how much in a year, call it x percent = 100 (x/9000)

*January 5, 2017*

**Maths**

By the way for small angles most of us assume sin theta = tan theta = angle in radians where angle in radians = angle in degrees * pi/180 then the arc length = chord length = R theta

*January 5, 2017*

**Maths**

LOL, If you really want to do it as an isoceles triangle with equal legs of length 5.06 e13 miles then sin .5 minutes = (x/2)/5.06e13 x = 5.06 e13 * 2 sin .5 min sin .5 min = sin (.5/60) degrees = .000145441 times 10.12 e13 = .00147186292 e13 = 1.47 e10 again:)

*January 5, 2017*

**my typo**

found error so your arc length in light years is 2 pi(8.611)/(60*360) = .0025048 light years which is 1.47e10 miles (those are land, not nautical miles) To get it go to Google and type .0025048 light years = miles and hit enter or use calculator and speed of light.

*January 5, 2017*

**Maths**

Clearly parallax is not a problem at this distance :)

*January 5, 2017*

**Maths**

You are right, I have an arithmetic error I estimate that 8.6 light years ia about 5.06 * 10^13 or 5.06e13 miles one minute is 1/21,600 of the circumference [ that is 1/(360*60) because 360 degree and 60 minutes per degree] circumference = 2 pi r = 2 pi * 5.06e13 = about 31 ...

*January 5, 2017*

**Maths**

for that pesky e notation: http://www.mathsisfun.com/numbers/scientific-notation.html look at example at the end: Example: 3.12E4 is the same as 3.12 × 104 3.12E4 = 3.12 × 10 × 10 × 10 × 10 = 31,200

*January 5, 2017*

**Maths**

Oh my, you really need another bit of spherical trig, namely the measure of an angle in "radians" there are 2 pi radians in a circle of 360 degrees so the circumference is C = 2 pi radians * R the handy thing is for any angle in radians now arc length along circle = ...

*January 5, 2017*

**Maths**

2*1.5 = 3 m^2

*January 5, 2017*

**physics (mechanics)**

dU = work done=potential change or force dr = dU U = A/r dU/dr = F = -A/r^2 Sign of A depends on attractive or repulsive.

*January 5, 2017*

**Pre Calc**

These are straight lines, they cross once. 2.4 +.3 t = 1.1 + .7 t .4 t = 1.3 t = 13/4 = 3 1/4 years

*January 4, 2017*

**Math**

pre tax = 1.18 p 1.18 p * 1.06 = 37.20 so p = 37.20 / (1.18*1.06)

*January 4, 2017*

**math - calculus help!**

oh well, not that hard V = (1/3)pi r^2 h r = 7 h/24 so V = (1/3)pi (7/24)^2 h^3 dV/dh = pi (7/24)^2 h^2 dh when h = 10 dV = pi (70/24)^2 dh dV = pi (35/12)^2 dh

*January 4, 2017*

**math - calculus help!**

You could use a fancy formula for volume of a cone and differentiate it to find dV/dh but if you just draw a picture you can see that the area of the surface * dh is the added volume for added dh

*January 4, 2017*

**math - calculus help!**

radius/depth = 7/24 what is radius when depth = 10? 7/24 = r/10 r = 70/24 = 35/12 now the change of volume with depth h is the surface area area * dh = dV pi r^2 dh = dV pi r^2 dh/dt = dV/dt = 12 ft^3/m pi (35/12)^2 dh/dt = 12 dh/dt = .449 ft/min

*January 4, 2017*

**Pre calc**

Good, you have two different ways now :)

*January 4, 2017*

**Pre calc**

slope = (20-13)/(4-3) = 7 also for any (x,y) slope = (y-20)/(x-4) so 7 = (y-20)/(x-4) 7 x - 28 = y - 20 so y = 7 x -8

*January 4, 2017*

**THANK YOU DAMON**

You are welcome :)

*January 4, 2017*

**Social Studies**

a.They conquered inland kingdoms, which they turned into a trading empire. --------------- The big advantage the Portuguese had over Arabs etc in the Indian Ocean was big ships with big guns. They did not try to march inland. India was a civilized country with real armies, not...

*January 4, 2017*

**Social Studies**

Yes, maybe b then c

*January 4, 2017*

**Social Studies**

It was particularly the various competing Christian missionaries that made the Japanese mad, and they were very angry about what happened in the Phillippines. The Dutch were allowed to hang out in a Nagasaki trading post because they did not try to convert people or push them ...

*January 4, 2017*

**Social Studies**

Particularly this excerpt: "Japan had been closed to the outside world for 250 years. When foreign people entered Japanese waters, even if they were shipwrecked by accident, they were interned in jails and some of them were killed (Lubor 33). The reasons for the Japanese ...

*January 4, 2017*

**Social Studies**

Ah yes, this is short and sweet http://willamette.edu/~rloftus/perry.html

*January 4, 2017*

**Social Studies**

I am looking for a link for question 2

*January 4, 2017*

**Social Studies**

no, no

*January 4, 2017*

**Social Studies**

Now for question 2, perhaps we better look at the start of American-Japanese relations. Did you read about only the Dutch being allowed there before that fleet arrived?

*January 4, 2017*

**Social Studies**

here is a wiki for Goa: http://www.google.com/search?q=goa+india&ie=utf-8&oe=utf-8

*January 4, 2017*

**Social Studies**

Well, I suppose I could give you some link to a wiki or something, but first think about it. The Portuguese ended it all in India long this after with Goa. Can you imagine a little country like Portugal marching around India ? They were sea farers

*January 4, 2017*

**Social Studies**

In question 1, remember we are talking about the Portuguese, not some tea company.

*January 4, 2017*

**Social Studies**

Ah, what do you think? The answer to question 2 is petty dramatic and amazing.

*January 4, 2017*

**Pre calc**

y = m x + b y = -(3/2) x +3/4 or 4 y = -6 x + 3

*January 4, 2017*

**History**

Well, my choices would be: 1. Prince Henry the Navigator, Bartolomeu Dias, Vasco da Gama .... so D 2.I would say B 3. See question 1.

*January 4, 2017*

**Math**

65*50 = 6500/2 = 3250 ft^2 so 1625/3250 $/ft^2

*January 4, 2017*

**American Government**

County responsibility is now chiefly law enforcement (sheriff and county jail) and registry of deeds and such. However it still exists and the towns and cities have not take over all county responsibilities.

*January 4, 2017*

**American Government**

Although our ounty government has been largely eliminated over the last decade, we still have a sheriff etc. Our town governments operate much like our city governments, although often having a Board of Selectmen instead of a City Council. Both towns and cities are often run ...

*January 4, 2017*

**American Government**

http://en.wikipedia.org/wiki/Essex_County,_Massachusetts

*January 4, 2017*

**Physics**

I think it is a dip and v^2/R = 0.15*9.81

*December 30, 2016*

**Physics**

density = 1000 kg/m^3 is easier :) You do not say if you want gage pressure or absolute pressure I will assume gage rho g h = 1000*10*25 =2.5 *10^5 Pascals or N/m^2 if you want absolute pressure add one atmophere or about 1*10^5 for a total of 3.5*10^5 Pascals

*December 30, 2016*

**Physics**

You already said the speed of the boat through the water was 2 m/s The speed over the land is 2-.8 = 1.2 m/s

*December 30, 2016*

**physics**

v^2/R = g or it loses contact m g(h-D) = .5 mv^2 v^2 = g R = .5 g D so m g(h-D) = .5 m *.5 g D =.25 mgD h-D = .25 D h = 1.25 D

*December 30, 2016*