Monday

July 25, 2016
Total # Posts: 26,544

**Pre Cal**

assume you mean x^2 + y^2 = 0 That is a circle of zero radius with center at the origin :) In other words a dot at the origin.
*February 25, 2016*

**Science**

Looks like it reacted chemically with something in the air to me :)
*February 25, 2016*

**math**

first one black = 26/52 = 1/2 second one black = 25/51 third one black = 24/50 fourth one black = 23/49 etc until we get to number 12 then multiply all those fractions that means you got every king, queen and jack 4 kings + 4 queens + 4 jacks = 12 of the 52 card 1 = 12/52 ...
*February 25, 2016*

**MATH**

3 x - y = 4 3 x - y = 6 never cross -parallel, no solution 2 x - y = 1 3 x + y = 6 --------------add 5 x = 7 x = 7/5 etc 1 x - 5 y = 5 3 x + 1 y = 7 multiply first by 3 3 x -15 y = 15 3 x + 1 y = 7 ---------------subtract -16 y = 8 y = -1/2 etc
*February 24, 2016*

**Math**

21 * 7 = (1 - 5/8) p = (3/8) p p = 49*8 = 382 pages
*February 24, 2016*

**Algebra**

y = - x^3 no y = -3^x would be but not this
*February 24, 2016*

**Algebra: Check Answer**

LOL no need to ask, plug back in h = -16(10.4)^2 + 156(10.4) +105 = -1730.56 + 1622.4 + 105 = -1730.56 + 1727.4 close enough to the ground :)
*February 24, 2016*

**Math**

Yes dA/dr = 2 pi r = 6.28 r correct however think a little more dA = 2 pi r dr = circumference * dr If you draw a picture of a circle r and then one outside it with radius r + dr You will see immediately that the change in area is the strip of length 2 pi r times the width dr
*February 24, 2016*

**Math**

dA = 2 pi r dr yes, correct however notice that this is simply the circumference the new area added is the circumference * dr
*February 24, 2016*

**math**

Yes we agree but I simplified
*February 24, 2016*

**math**

I assume dy/dx=(4sqrt(y)ln x)/x y^-.5 dy = 4 (ln x /x)dx y^.5 = 2 [ .5 ln^2 x ] y^.5 = ln^2 x y = ln^4 x + c
*February 24, 2016*

**Physics**

bullet momentum = .017 v total mass = .017+1.2 = 1.217 kg final momentum = initial momentum .017 v = 1.217 V' V' = .014 v normal force on table = m g = 1.217 (9.81) friction force = .23*1.217*9.81 = 2.75 Newtons work done = 2.75 *8.6 = 23.6 Joules so 23.6 =(1/2)mV'...
*February 24, 2016*

**Algebra 2**

yes all 3 are correct but it is easier to use sin and cos sin^-1 (3/19) and cos^-1 (18.8/19)
*February 24, 2016*

**ALGEBRA**

surface area = area of top + area of bottom + area of side = pi r^2 + pi r^2 + 2 pi r h = 2 pi (r^2+ r h) = 2 pi r (r + h) = 2 *pi*4 * 10 = 80 pi volume = pi r^2 h = pi *14 * 6 = 84 pi
*February 24, 2016*

**Math**

let z = y^.5 then dz = .5 y^-.5 dy dy = 2 y^.5 dz = 2 z dz 2 z dz /(z cos^2 (z) ) = x dx dz/( cos^2 (z)) = .5 x dx tan z = .25 x^2 + constant tan y^.5 = .25 x^2 + constant
*February 24, 2016*

**Mensuration**

Now I showed you how to do one by subtracting rectangles. You do this one.
*February 24, 2016*

**Math**

That is quite a markup : I have a sneaking suspicion that they mean 140% markup but will do it as stated .75 * price = 39.95 so usual price = 53.27 cost + 2.40 * cost = 53.27 3.40 * cost = 53.27 cost = 15.67 39.95 - 15.67 = 24.28
*February 24, 2016*

**Trigonometry**

m and j tan 30 = m/15 tan 45 = 1 = j/15 j - 15 and m = 15 tan 30 = 8.66 m+j = 23.7
*February 24, 2016*

**Precalculus**

sec 4x = 1/cos 4x I can not graph it for you here but note that cos 90 or pi/2 = 0 so you are going to have a bunch of vertical asymptotes
*February 24, 2016*

**Mensuration**

the original sheet is 30*20 = 600 cm^2 the remaining sheet is 30-8 by 20-8 or 22 * 12 = 264 cm^2 so you removed: 600 - 264
*February 24, 2016*

**Calculus**

pi/3 = 60 degree just so I do not have to use radians on my calculator :) c^2 = a^2 + b^2 - 2 a b cos C get initial stuff first cos 60 = 1/2 sin 60 = .866 c^2 = 64 + 169 - 208 cos 60 c^2 = 233 - 104 = 129 c = 11.4 now do the problem 2 c dc/dt = -208 (-sin 60) dC/dt so dc/dt = ...
*February 24, 2016*

**Math**

i = -75 p^2 + 600 p if p = 3 i = -75 (9) + 1800 1,125 = -75 p^2 + 600 p 75 p^2 -600 p + 1,125 = 0 solve quadratic for 2 values of p. Throw out any negative one etc for max I assume you do not know calculus so complete square to find vertex 75 p^2 - 600 p = -i p^2 - 8 p = -i/75...
*February 24, 2016*

**statistics**

I will do three cards, you do five. 52 cards, 26 are red so find probability of all black first draw 26/52 = 1/2 second draw 25/51 third draw 24/50 = 12/25 prob of all black =.5*25/51*12/25 =.118 so 1-.118 = .882 for at least one red in three draws
*February 24, 2016*

**physics- check this out**

v = Vi + a t v = 0 at stop a = -Vi/t = -35 m/s^2
*February 24, 2016*

**Physics**

7 t = d 13 t = d+42 so 6 t = 42 t = 7 7 t = d = 49
*February 24, 2016*

**physics**

A kilowatt is 1,000 Watts
*February 24, 2016*

**Physics**

I will have to guess at your drawing. Both objects fall the same. The first one keeps its horizontal velocity so both fall 1.14 meters v = g t = 9.81 t 1.14 = (1/2) g t^2 = 4.9 t^2 so t = 0.482 second fall time for both so vertical velocity of both is 9.81 * .482 = 4.73 m/s ...
*February 24, 2016*

**physic**

falls 63 m 63 = 4.9 t^2 calculate t which is time in air now range = 20 t the end.
*February 24, 2016*

**physics**

Kilo
*February 24, 2016*

**physics**

22.61 g/cm^3 * (100 cm/m)^3 (1kg/1000g) = 22,610 kg/m^3 by the way water is about 1000 kg/m^2
*February 24, 2016*

**????**

You forgot the equation
*February 24, 2016*

**physics**

20 east
*February 24, 2016*

**physics**

I assume you mean 8 hours. Velocity is the displacement /time and direction Here that is 320/8 or 40 mph North The 400 zigging and zagging is irrelevant for velocity but important if you wanted speed instead of velocity
*February 24, 2016*

**please help**

Please just do what I suggested. Goggle Mt Kilimanjaro and those countries.
*February 24, 2016*

**African climates - where to start?**

I do not know what to say. Except for one mountain (http://www.tanzaniaparks.com/kili.html) there is not much snow. However everything else is there :) Desert in the North, riverine in the Nile valley, jungle in the center and down the Congo river. Savannas, farmland, grazing ...
*February 24, 2016*

**science**

when the potential (voltage) is different in different places on the conductor.
*February 21, 2016*

**Science**

It doubles every (1/4) day? in 7 days it doubles 28 times 2^28 = 268,435,456
*February 21, 2016*

**Science**

Maybe you mean Bernoulli : (1/2)rho v^2 + rho g h + p = constant If flow is constant in time and no frictional losses rho = density h = altitude p = pressure g - gravitation acceleration v = speed
*February 21, 2016*

**Physics**

I can not sketch it for you. v = (2t+1.34) i + 3.34 j + (6t^2 - 8t) k so put in t = 2 a = 2 i + (12t-8) k again use 2 for t
*February 21, 2016*

**Physics**

A: v = 10 pi/(10.34) Ac = v^2/r = 20 pi^2/(10.34)^2 B: v = 20 pi/(10.34) Ac = 40 pi^2/(10.34)^2
*February 21, 2016*

**Maths**

(-4/3) x = 16/3 -4 x = 16 x = -4
*February 21, 2016*

**science**

60min/hr * 60 sec/min = 3600 seconds/hour 2 * 3600 + 35 = 7235
*February 21, 2016*

**Chemistry**

we are close to STP here where one mol is 22.4 liters 58.4/22.4 is around 2.61 moles 10.3/2.61 = 3.95 grams/mol Helium maybe ?
*February 21, 2016*

**Algebra**

Oh well, I'll play 300 = k * 3^2 * 10.62 so k = 300/(9*10.62) = 3.14 remarkable :) in fact v = pi r^2 h = pi * 3^2 * 10.62 = 300.27 :) so we say v = 3.14 * r^2 *h = 3.14 * 16 * 15.92 =785 cm^3
*February 20, 2016*

**Physics**

horizontal rope force= 100 cos 60 = 50 N so a) work done by tension = 50*15 = 750 Joules b) NONE !!!! there is no vertical displacement !
*February 20, 2016*

**Math**

.6 (299) = 179.4
*February 20, 2016*

**math**

I guess you mean circumference of a circle of radius 5.5 in if so 2 pi r = 11 pi
*February 20, 2016*

**High school calculus**

I have a extra b in there.
*February 20, 2016*

**High school calculus**

dy = (bx+5)^-3 dx let z = bx+5 then dz = b dx and dx = (1/b) dz dy = (1/b) z^-3 dz y = (1/b)(-1/2)z^-2 + c y = -1/(2b z^2) + c but z^2 = b^2x^2 + 10 bx + 25 so 2 b z^2 = 2b^3x^2 + 20 b^2 x + 50 b so y = -1/(2b^3x^2 + 20 b^2 x + 50 b) + c
*February 20, 2016*

**Algebra**

t = k r^2/z^3 4 = k 36/27 k = 3 so t = 3 r^2/z^3 ============================ c = k d^2/L .54 mho = k 3^2/50 k = 50 * .54 /9 = 3 again LOL (note - in your units which are not the ones a physicist would tend to use)
*February 20, 2016*

**math**

Some blame it on people like Pythagoras but I think folks along the Indus River thought it up to keep track of monsoons and crops and water level and stars and stuff. The really important guy was Sicilian but everyone calls him Greek named Archimedes. He not only figured out ...
*February 20, 2016*

**phy 231**

centripetal acceleration Ac = v^2/r = r omega^2 omega is part a r = radius there = Re sin 49 [ note - usually we use latitude which is angle North of the equator in this case cos(90-49)]
*February 20, 2016*

**physics**

(1/2) a t^2 = h (1/2)(9.81)(36) = h in meters
*February 20, 2016*

**math**

I can guess based on the possible answers. The only one with a y axis intercept is y = 5 x + 2 that is $2 to walk in the store and a unit rate of $5 per sandwich
*February 19, 2016*

**Statistics**

You are welcome.
*February 19, 2016*

**Statistics**

http://davidmlane.com/hyperstat/z_table.html
*February 19, 2016*

**Math**

http://www.jiskha.com/display.cgi?id=1455913440
*February 19, 2016*

**Just did it**

see below
*February 19, 2016*

**Math**

.80 * .75 * 179.99
*February 19, 2016*

**physics**

work output = 500 * 1.7 = 850 Joules work input = 1000 Joules efficiency = (850/1000)100 = 85 % since you did not say what the velocity ratio was, how would I know what the mechanical advantage was? They are the same on inverses depending of which way you write the velocity ...
*February 19, 2016*

**chemistry**

if they have more than one electron or lack of electrons in complete outer shell they can lose or gain electrons to form complete outer shells. Google oxidation reduction
*February 18, 2016*

**Physics**

100,000 meters/3600 seconds = 27.8 m/s d = 27.8 t d = (1/2)(3)(t-20)^2 so 18.5 t = t^2 -40 t + 400 solve quadratic for t
*February 18, 2016*

**Chemistry**

You do not say if you are in middle school, high school or college or what you are having trouble with. Google chemistry and you will find lots of stuff, for example: http://www.learnerstv.com/Free-chemistry-Video-lectures-ltv558-Page1.htm
*February 17, 2016*

**huh?**

Missing info, perhaps width of frame
*February 17, 2016*

**Physics/Eletrical engineering**

That is called a circuit.
*February 17, 2016*

**Chemistry**

5 grams of Na is 5/23 = .2174 mols so we get .2174 mols of NaBr NaBr = 23 + 80 = 103 grams/mol .2174 * 103 = 22.4 grams
*February 17, 2016*

**Physics**

http://www.jiskha.com/display.cgi?id=1455744206
*February 17, 2016*

**Physics**

Been there, done that. Check below
*February 17, 2016*

**Calculus**

If the first then dM/dt = -(1/3)(2t) + 1 = -2t/3 + 1 if t = 2 dM/dt = -4/3 + 3/3 = -1/3 the medicine is disappearing, presumably because it is eating bad guys.
*February 17, 2016*

**Calculus Please use parentheses**

-(1/3) t^2 + t or -1/(3 t^2) + t or 1/(3t^2+t)
*February 17, 2016*

**math, simple math**

which is e^(-x^2/a^2)
*February 17, 2016*

**Physics**

up 1 cm on 51 cm string cos A = 50/51 sin A = side force F/ Tension T tan A = F/(mg) so F/mg = tan 11.36 = .201 F = .001 (9.81)(.201) = .00197 Newtons F = Q E .00197 = Q * 9200 Q = 2.14 * 10^-7 Coulomb If motion in direction of E field, charge positive
*February 17, 2016*

**physics**

The center of mass will not accelerate, no external force on the system. That is a distance d from the 6000 kg asteroid 6000 d = 3580(400 -d) 6000 d = 1,432,000 -3580 d d = 149.5 meters from the asteroid so we need to pull the asteroid 149.5 meters 149.5 = (1/2) a t^2 where a...
*February 17, 2016*

**math age problem**

(r-2) , r , (r+8) 3 r + 6 = 60 3 r = 54 r = 18 so 16 , 18 , 26
*February 17, 2016*

**whoops**

sorry, use Reiny solution
*February 17, 2016*

**Trig**

cos 52 = (h-10.5) /12
*February 17, 2016*

**algebra**

one triangle is 20 by 30 the other is 30 by 30 sqrt(30^2+30^2) + sqrt(20^2+30^2)
*February 17, 2016*

**chemistry**

well, first it only has one electron. The spectrum gives you possible energy levels (states or orbit radius) for that electron.
*February 16, 2016*

**math**

h = 1000 x = sqrt (1250^2 - 1000^2) = 750 meters horizontal r = distance (hypotenuse) r^2 = h^2 + x^2 2 r dr/dt = 0 + 2 x dx/dt so dr/dt = (x/r) dx/dt = (750/1250)(800)
*February 16, 2016*

**math**

38 = 2 * 19 57 = 3 * 19 so 2/3
*February 16, 2016*

**Algebra**

Yes, an hour, 60 min
*February 16, 2016*

**Algebra**

stan speed = s lawns/min Hilda speed = 2s lawns/min (s + 2s) = total speed in lawns/min so (s + 2s) (20 min) = 1 lawn 60 s = 1 s = 1/60 lawns/min or 60 min/lawn
*February 16, 2016*

**Algebra**

80 t = 125 (t-1) 125 = 45 t t = 2.7777 hours or 2 hours and 47 min for car 1 and 1 hour and 47 minutes for car 2 check 80 * 2.777 = 222 125 * 1.777 = 222 good so 1 hour and 47 minutes
*February 16, 2016*

**Algebra**

420 - 20 = 400 420 + 5 = 425 so 400</= T </= 425
*February 16, 2016*

**Algebra**

8 parts total (3/8)(568) alcohol (5/8)(568) acid
*February 16, 2016*

**Algebra**

.04 x + .06 ( 67000-x) = 3440
*February 16, 2016*

**math**

I guess it starts at 0 height h = a x^2 + b x 148 = a (1)^2 + b(1) 272 = a(2)^2 + b(2) b = 148 - a 272 = 4 a + 2 (148-a) 272 = 4 a -2 a + 296 2 a = -24 a = -12 (should be 16 on earth but anyway) b = 148 +12 = 160 so h = -12 x^2 + 160 x if x = 6 h = -12*36 + 160(6) = 528
*February 16, 2016*

**Algebra**

f = 4 t 5 f + 10 t = 1050 so 20 t + 10 t = 1050 30 t = 1050 t = 35 tens
*February 16, 2016*

**Help please? Math 141 (Pre-Cal)**

as t gets huge the 84 and the 28 are small potatoes s ---> 51/3 = 17 16.5 = (51 t + 84)/(3t+28) solve for t
*February 16, 2016*

**Math**

are you doing geometric sequences maybe? 32 32*4.5 32*4.5^2 32*4.5^3 32 144 648 2916
*February 16, 2016*

**Physics**

Torque = I alpha Tension in line = T weight = m g = 1 * 9.8 = 9.8 N so 9.8 - T = 1(4.5) T = 5.3 N or kg m/s^2 torque = T * R = 5.3 R Nm or kg m^2/s^2 so 5.3 R kg m^2/s^2 = I alpha but a = alpha R so alpha = a/R so 5.3 R^2 kg m^3/s^2 = I kg m^2 * 4.5 m/s^2 I = 5.3 * .45^2 /4.5...
*February 16, 2016*

**physics**

assuming that then v = dx/dt = 2 A t + B a e^(at) acc = dv/dt = 2 A + B a^2 e^(at) now constraints at t = 0 -2 = B so 4 = -2 a a = -2 so in fact x = A t^2 -2 e^(-2t) v = 2 A t + 4 e^(-2t) acc = 2 A -8 e^(-2t) now at t = .2 , v = 5 so 5 = 2 A(.2) - 8 e^-.4 5 = .4 A - 5.36 A = ...
*February 16, 2016*

**?**

do you mean x = A t^2 + B e^(at) ?
*February 16, 2016*

**Social Studies (Check, Please!)**

Typo in #2 fight, they were old enough to fight. You mean VOTE
*February 16, 2016*

** jewellry**

Amma said to do what she typed, y = -3/x + 1
*February 16, 2016*

**Math-asymptotes**

ok if it is y = -(3/x) + 1 then clearly when x -->0 this becomes huge positive or negative depending on if x is positive or negative. That is the poit of vertical asymptotes as x becomes huge positive or negative, y---> 1 horizontal
*February 16, 2016*

**huh?**

do you mean y = -3/(x+1) or what you typed?
*February 16, 2016*

**Math**

2 cups / 36 cookies = x cups/ 60 cookies
*February 16, 2016*

**Math**

cran/gran = 1/3 1/3 = 3/x x = 9
*February 16, 2016*

**Algebra**

24.5 * 10^4 = 2.45 * 10^5 so yes, b
*February 16, 2016*