Thursday

June 30, 2016
Total # Posts: 26,400

**Calculus,Stationary Points,First derivative test**

You say dy/dx = 6(x^2 - x - 2) so the function is horizontal when (x-2)(x+1) = 0 or x = 2 and x = -1 Agreed NOW you can test it like you did, but usually what you do is take the second derivative. If it is +, the function is at the bottom and about to start up. If it is ...
*January 17, 2016*

**Maths**

Hey, try I will do D 3 sqrt 18 = 3 sqrt (9*2) = 3 sqrt (3*3*2) = 3*3 sqrt 2 = 9 sqrt 2 = 9 (1.414) around 12.5 or so which is between 12 and 13 NOW check that with your calculator (Google calculator if you do not have one on your desk) 3 sqrt(18) = 12.728
*January 17, 2016*

**ah I do not think so !**

8+3+5 = 16 not 11 so 3/16
*January 17, 2016*

**chemistry**

25 + 273 = 298 degrees Kelvin P V = n R T n and R are constant You do not mention P, so I guess maybe the pressure is constant? V/T = n R/P = constant so V1/T1 = V2/T2 T2 = (V2/V1) T1 T2 = .5 T1 = 298/2 = 149 K -273 + 149 = - 124 C That is wicked chilly.
*January 17, 2016*

**physics**

DRAW A PICTURE The way I am looking at it: speaker at x = -6 speaker at x = +6 wave from left at x = -6 moves right y = sin (w t - 2 pi x/L) wave from right at x = + 6 moves left y = sin (w t + 2 pi x/L) at x y=sin(wt-2pi x/L)+sin(wt+2pi x/L) = 2sin(wt)*cos(2 pi x/L) This is ...
*January 17, 2016*

**algebra ,**

ends in 5 or 0 odd, so ends in 5 100 a + 10 b + c We know c = 5 100 a + 10 b + 5 a b 5 = 15 or a b = 3 a + b <5 100a + 10 b < 144 so a = 1 since a b = 3, b = 3 so 135
*January 17, 2016*

**GCU**

Well, it does not, but anyway W = k * L 162 = k * 9 k = 162/9 then W = k * 8 W = (162/9) 8 W = 144 Problem is, unlike in math class, when you make a boat longer you have to make it stronger and wider and deeper so in real life it is closer to W = k * L^3
*January 17, 2016*

**Physics**

heat the ball warms up and the ground warms up, but not much :)
*January 17, 2016*

**geometry**

You are welcome.
*January 16, 2016*

**geometry**

there are 360 degrees in a circle there are 2 pi radians in a circle therefore: multiply radians by (180 deg/pi radians) to get degrees :)
*January 16, 2016*

**Mathematics**

dy/dx = [x^4 e^x - 4 x^3 e^x]/x^8 = [ x e^x - 4 e^x ] / x^5 = 0 when x = 4 increasing if x>4 decreasing if x <4 what is sign of second derivative? It is a pain to compute, sketch graph of slope' http://www.wolframalpha.com/input/?i=plot+[+x+e^x+-+4+e^x+]+%2F+x^5 sure...
*January 16, 2016*

**Math**

do you mean y = e^rx ? r^2 e^rx + 5 r e^rx + 6 e^rx = 0 r%2 + 5 r + 6 = 0 (r+3)(r+2) = 0 r = -3 or -2
*January 16, 2016*

**World History**

The wrong ones are so terribly, horribly wrong and the right one is horribly correct :(
*January 16, 2016*

**Math Terminology**

3 , 2 , and 7 are constants
*January 16, 2016*

**Algebra/math**

It is not possible for you to copy and paste to this site. Therefore we do not see your origimi.
*January 16, 2016*

**same gibberish. Read what you typed**

and also read my previous reply 5.11 %
*January 16, 2016*

**Math**

.1 * 23 = 2.3 half of that = 1.2 sum = 3.5 so I agree
*January 16, 2016*

**gibberish**

7000 days? 18 months? what are you talking about? anyway .05/12 = .004167 so every month multiply by 1.004167 so in twelve months v = Vi (1.004167)^12 v = Vi * 1.0511 or 5.11 percent annual interst
*January 16, 2016*

**TYPO muzzle speed far too low to ever work, wrong.**

Vi = initial up speed = ? cos A u = constant horizontal component = ? sin A s = horizontal airplane speed=340 T = flight time for both horizontal problem: 340 T = u T = ? T sin A so sin A = 340/(? ) which is kind of obvious :) now the vertical problem: h = 0 + Vi t -.49 t^2
*January 16, 2016*

**math**

v = 12,500 * .85^n
*January 16, 2016*

**math TYPO**

do you mean 40 cm^2 ? I will assume so A = (1/2) b h since it is 90 degrees, h is altitude , other leg 4 h = 40 h = 10 cm so we still need the hypotenuse c^2 = h^2 + b^2 = 100 + 64 = 164 = c = 2 sqrt (41) = 12.8 cm
*January 16, 2016*

**Math**

Lemme see 9 + 16 = 25 sure enough 2.5 * 9 + 3.25 * 16 = 74.5 which you could have done. If you are stuck, ask for help. If you need an answer checked, first check it.
*January 16, 2016*

**Geometry(Check My Answers)**

yes 30 + 75 + 75 = 180 You choice is ok the rest are not 7 and 13 will not reach 22 6 12 18 is a straight line again 13 + 8 = 21, will not reach
*January 15, 2016*

**Math**

3 + 16/25 = 3.64 3.64 * 100 = 364 yes, agree
*January 15, 2016*

**Geometry**

No, I can not explain that because I agree with you either by side angle side or as you said by the angles
*January 15, 2016*

**Mechanics(Ms.Sue)**

efficiency is maximum 100%, and that is impossible. Output less than input D is correct Yes !!! for speed you need a speedometer for velocity you need a speedometer AND a compass speed = scalar velocity = vector
*January 15, 2016*

**Math**

try 1600/75
*January 15, 2016*

**Math**

You do not get 85 if you divide 17 miles / 20 minutes You get 0.85 miles/minute mph is wrong here. Hours is not in the problem
*January 15, 2016*

**Careful !!**

2. x/5 + 6 = 10 a) 44 b) 30 <----------- c) 20 d) –20 ======================= x/5 = 4 x = 5 * 4 x = 20 I do not have time to look at all of them but for heavens sake try checking by substituting back in using x = 20 x/5 + 6 = 10 20/5 + 6 = 10 ? 4 + 6 = 10 YES - I got ...
*January 15, 2016*

**Quadratic Equation (math)**

well, 36 = 6^2 so try x^2 + b x + 36 = (x+6)^2 x^2 + b x + 36 = x^2 + 12 x + 36 so x^2 + 12 x + 36 ------------------- more officially (b/2)^2 = 36 b/2 = 6 b = 12
*January 15, 2016*

**Math**

150,000 $/sec * t sec = 3,000,000 t = 3,000 / 150 t = 20 seconds Again, nothing about minutes here, all is in seconds Of course we happen to know that 20 seconds is 1/3 of a minute :)
*January 15, 2016*

**Math**

4,500,000 /30 = 150,000 No, there is nothing about minutes in this problem
*January 15, 2016*

**Math help plz!!**

Look, I get 676 people. That is not on your list. Either you have a typo or your book does or I am stark raving mad.
*January 15, 2016*

**Typo maybe?**

1/3 * 1092 = 364 2/7 * 1092 = 312 364 + 312 = 676
*January 15, 2016*

**Math**

Now #10 10. –3p > –48 a) p < 16 b) p > –51 c) p < –16 <------------ d) p > 16 ====================== –3p > –48 divide both sides by -3. When you multiply or divide by a negative, REVERSE the arrow p < 16 WHICH IS A I do not...
*January 15, 2016*

**Math**

Oh all right, number 1 YOU SAY B ? 1. –9x – 5 = –95 a) 17 b) 11 <--------------- c) 10 d) –10 ===let me see =========== - 9 x - 5 = - 95 add 5 to both sides - 9 x = - 90 multiply both sides by -1 9 x = 90 divide both sides by 9 x = 10 which is not 11
*January 15, 2016*

**history**

As Ms. Sue said, your answer depends on your point of view.
*January 15, 2016*

**history**

Not C
*January 15, 2016*

**GOT IT ????**

That is important.
*January 15, 2016*

**Algebra**

f(x+h) = 4(x+h)^2 + 9 f(x) = 4 x^2 + 9 -----------------subtract delta y =4[x^2 + 2 x h + h^2 -x^2] = 4 (2 x h + h^2) delta x = h so delta y/delta x = 4(2x + h) END OF YOUR PROBLEM Oh my look what we have here as h ---> 0 !! delta y/delta x --> 4 (2x) That is called the ...
*January 15, 2016*

**Algebra**

Oh, I do not know what your belief means but I know what x+h and f(x+h) means. They are trying to lead you to calculus
*January 15, 2016*

**Algebra**

y(r) = 4 r^2 + 9 = u y(c) = 4 c^2 + 9 = g ----------------------subtract y(r)-y(c) = 4(r^2-c^2) = u-g =delta y delta x = (r-c) delta y/delta x = 4(r^2-c^2)/(r-c) = 4(r+c) I do not understand B
*January 15, 2016*

**Math**

5 * (n + 17 ) </= 25 so what is the problem? Just replace words with symbols.
*January 15, 2016*

**MATH NEED HELP ASAP!!!!!**

You said B I showed you that B is impossible.
*January 15, 2016*

**MATH NEED HELP ASAP!!!!!**

Hey in six years Henry's age will be H + 6 and Justin's age will be J + 6 so B simply is a non-starter
*January 15, 2016*

**MATH NEED HELP ASAP!!!!!**

So which one is your choice?
*January 15, 2016*

**Science (physics)**

P V = n R T n is proportional to number of gas molecules in the bag, remains constant here R is constant So P V/T is constant If T goes up, then P V goes up so likely the balloon gets bigger (stretches) and / or the pressure goes up
*January 15, 2016*

**AP Physics 1**

north = 21 - 26 = - 5 east = 16 distance = sart (5^2+16^2) on x y axis system tan h = -5/16 h = -17.35 so 17.35 degrees below x axis which is a compass bearing clockwise from north of 17.35 + 90 = 107.35 about ESE
*January 15, 2016*

**Math**

What is the experimental probability of rolling a 3? A.0.11 B.0.22 C.0.30 D.0.27 ================ 11/50 = 22/100 = .22
*January 15, 2016*

**Math**

I counted 3 out of 20 Yes, you have it
*January 15, 2016*

**Math ASAP ASAP!!!!!**

yes 80/.2 = 800/2 = 400
*January 15, 2016*

**Geometry**

9 inches * (1 foot / 12 inches ) = .75 foot so 5.75 / 2 = h/7 multiply both sides by 14 5.75 * 7 = 2 h h = 7.75 * 7/2 h = 27.125 which is 27 1/8 feet which is 27 feet 1 and 1/2 inches :)
*January 15, 2016*

**Math**

What is the y-intercept of y = 2/3x + 2? I have to write it out but how? ------------------------------ The y axis intercept is where x = 0 which in this case is 2 and I think you meant to type y = (2/3) x + 2 because what you typed was y = 2/(3x) + 2 think parentheses when ...
*January 15, 2016*

**PHYSICS**

Beats me, but if they go faster than light they can do about anything.
*January 15, 2016*

**MATHS**

log ( 2^3 * 20/1.6) log (8 * 20/1.6) log 100 log 10^2 2 log 10 if these are base 10 logs then log10 = 1 so 2*1 = 2
*January 15, 2016*

**PHYSICS**

a photon has momentum but not mass. I am not sure "accelerate" has any meaning in this context. Of course the speed of light can change in different materials and its direction can change, but I am not sure I would call that "acceleration" (rate of change ...
*January 15, 2016*

**SCIENCE HELP PLS**

P V = n R T n/V is a proportional to density (molecules per unit volume) n/V = P/RT so either the temp went way up or the pressure went down You can pick the decrease in pressure.
*January 15, 2016*

**Algebra**

http://www.jiskha.com/display.cgi?id=1452879533#1452879533.1452880085
*January 15, 2016*

**Physics, and I just did it scroll down**

see problem below this one.
*January 15, 2016*

**Physics :)**

Vi = 13 m/s Hi = 1.0 m h = Hi + Vi t - 4.9 t^2 0 = 1 + 13 t - 4.9 t^2 now it is algebra 4.9 t^2 - 13 t - 1 = 0 t = [ 13 +/- sqrt (169 + 19.6)/9.81 use positive time :) t = 2.73 seconds (good hit, wow ! )
*January 15, 2016*

**united staes history**

We did not call them "slaves". They were "crew".
*January 15, 2016*

**Physics**

F = 543 - 473 = 79 N down on the student mass of student = 543/g a = F/m = 79 / (543/9.81) = 1.43 m/s^2 down
*January 15, 2016*

**Maths literacy and tourism,life science,geography**

Hermit
*January 15, 2016*

**Math**

Moreover it is not c :)
*January 15, 2016*

**ECE**

well it asks for the "drop", not just the difference so I guess I would say it dropped 5 However the question is poorly worded.
*January 15, 2016*

**Physics**

initial ke = (1/2)89.5(5.7)^2 + (1/2)81.5(2.58)^2 final ke = (1/2) 171 (v)^2
*January 14, 2016*

**Physics**

LOL, they clung to each other after so after the crash the total mass is 89.5 + 81.5 = 171 kg now east, the fullback I call +x initial momentum = 89.5*5.7 - 81.5*2.58 = 431 kg m/s final momentum = 171*v Newton #1 say those are identical so 171 v = 431 v = 2.52 m/s
*January 14, 2016*

**algebra**

q(21) = 6 - 5*21
*January 14, 2016*

**Math**

(2j+1) / (j+1)^2 j^2 ??? (2j+1) / (j^2 + 2 j + 1)j^2 (2 j + 1) / (j^4 + 2 j^3 + j^2) (2 j + 1) / (j^2 + 2 j^3 + j^4) try 12 25/( 144 + 3456 + 20736)= 25/24336 = .001027 this is going to get small fast the denominator will be totally dominated by j^4 and what we really will ...
*January 14, 2016*

**i need your help damon**

12.5 ft (.5 in/2 ft) = 3.125 in 11.5 ft (.5 in/ 2 ft) = 2.875 in so 2*3.125 + 2*2.875 = 12 in
*January 14, 2016*

**i need your help damon**

first of all look at what I did a minute ago for someone else: http://www.jiskha.com/display.cgi?id=1452820078
*January 14, 2016*

**physics**

You did not say if your angle T is measured from across or from upstream. I will do it from across x - along walk y across walk Vc = cat running speed Vx = Vc sin T - .5 = 0 for result we want Vy = Vc cos T so 0 = 1 sin T - .5 sin T = .5 T = 30 degrees Vy = 1 cos 30 = .866 if ...
*January 14, 2016*

**Conceptual Physics**

learn to convert like a physicist (not math way) 106 mm * ( 1) does not change anything BUT I claim that 10 millimeters /1 centimeter) is ONE, because it is the same top and bottom so what I do is: 106 mm (1 cm/10 mm) = 10.6 cm mm cancel and left with cm and 106 mm (1 m/1000 ...
*January 14, 2016*

**i really need help but dont know how to do it**

I have a million people to help, look up and down :)
*January 14, 2016*

**i really need help but dont know how to do it**

3.25 in (1 ft/.25 in) = 13 ft 2.75 (1/.25) = 11 feet area = 13 * 11 = 143
*January 14, 2016*

**Algebra**

s^2 = (5x - 3)(5x - 3) = (5x-3)^2 so s = 5x-3 when in danger or in doubt: http://www.mathportal.org/calculators/polynomials-solvers/polynomial-roots-calculator.php
*January 14, 2016*

**math**

2 L + 2 w = 38 so L + w = 19 and L = 19-w w L = 90 w (19-w) = 90 w^2 -19 w + 90 = 0 (w-9)(w-10) = 0 9 by 10
*January 14, 2016*

**geometry**

41 1/3 / 2 1/3 = 124 / 7 = 17.7 yards^2 / gal 17.7 * 9 = 159 ft^2/gal 275 - 159 = 116 difference
*January 14, 2016*

**Physics**

sin w t + sin x t = 2 sin.5(w+x)t cos.5(w-x)t beat frequency is omega = 2 pi f = .5(w-x) assume gum decreases x thereby increasing w-x so w is our 200 Hz fork w = 200*2 pi = 400 pi radians/s w - x = 5*2 pi = 10 pi so x = 390 pi = 195 Hz I suppose that is more than you wanted ...
*January 14, 2016*

**Physics**

Also, from 1.95 s to 2.05 s this is set up so you can compare your calculated speed with the real speed at 2 seconds from calculus. By coincidence we already did that last part, v(2) = 9.18 m/s and your average from 1.95 to 2.05 should be very close to that, like really, ...
*January 14, 2016*

**Physics**

well, just for fun, let's see hat the form of the limit is v = dx/dt = b + 3 c t^2 = 1.5 + 1.92 t^2 ========================= now from 1 to 3 x(3)= 1.5*3 +.64*27=4.5+17.28 = 21.78 x(1) = 1.5+.64 = 2.14 so x(3)-x(1) = 19.64 delta t = 3 - 1 = 2 seconds so v during interval...
*January 14, 2016*

**History**

I agree with you. Once every living soul did not have to hunt or gather, someone could stay behind and make shoes.
*January 14, 2016*

**Science**

I think it is B, but what do I know :)
*January 14, 2016*

**math**

64497 = .31 S S = 64497 /.31
*January 14, 2016*

**chemistry**

P V = n R T in this problem n, R and T are constant so P2 V2 = P1 V1 or in other words V2 = V1 (P1/P2) now do it
*January 14, 2016*

**Give us the whole problem**

Are you talking about a sequence? If so is it arithmetic? is it geometric? or what
*January 14, 2016*

**math**

first one y = -2x + 4 which is B m = -2 b = 4 second one y = 5 x + 8 which is A
*January 14, 2016*

**x and y reversed**

sorry, you have x and y reversed in the second one.
*January 14, 2016*

**math**

slope of -2. !!!!!!!!!! THAT means m = -2 in y = m x + b y = -2 x + b moreover you are told that when x = 0, y = +4 The second one is correct
*January 14, 2016*

**geometry h**

draw it y 4 --> 2 --> 0 because 4 to 2 is 2 which is 2 to 0 x 1 -->-3 --> -7 because 1 to -3 is -4 which is -3 to -7 (0, -7)
*January 14, 2016*

**Math**

1 2/4 + 1 3/4 = 2 5/4 = 3 1/4 5 - 3 1/4 = 4 4/4 - 3 1/4 = 1 3/4
*January 14, 2016*

**math**

y = (1/2) x + b 5 = (1/2) 0 + b b = 5 so y = (1/2) x + 5 which I guess you mean for A) but what you typed was y = 2/(2x) + 5
*January 14, 2016*

**Physics**

How long does it take to fall 0.52 meters? .52 = (1/2) g t^2 1.04 = 9.81 t^2 t = 0.326 seconds
*January 14, 2016*

**Science**

Sounds like here might be some steam with the Hydrogen Ions reacting with O2 :) However the scenario does not sound very likely.
*January 14, 2016*

**C s s oberkom**

frequency of 6 revolutions/second is a period of 1/6 seconds
*January 14, 2016*

**Do you mean?**

2 Na + 2 H2O --> 2 NaOH + H2 If so, what do you want to know?
*January 14, 2016*

**better grid to avoid error**

xx 1 2 3 4 5 6 -------------------- 1| 2 3 4 5 6 7 2| 3 4 5 6 7 8 3| 4 5 6 7 8 9 4| 5 6 7 8 9 10 5| 6 7 8 9 10 11 6| 7 8 9 10 11 12
*January 14, 2016*

**whoops 1/9 is right**

2. b is 4/36 = 1/9 you were right (I added in the top label five)
*January 14, 2016*

**Math**

1. a (1/2)^10 = 9.77*10^-4 = .000977 indeed 1/1024 b yes c yes 1 - 1/1024 = 1023/1024 2. lay the grid out x 1 2 3 4 5 6 1 2 3 4 5 6 7 2 3 4 5 6 7 8 3 4 5 6 7 8 9 4 5 6 7 8 9 10 5 6 7 8 9 10 11 6 7 8 9 10 11 12 a. yes, no up there :) b. 5/36 c. yes, lower right :)
*January 14, 2016*

**calculus 1**

first let's look at the derivative (slope at a point) y = 1/(1-x) dy/dx = slope = [-1(-1)]/(1-x)^2 bottom always + so the slope is always positive now secant from (2,-1) to ( x , 1/(1-x) ) secant slope P to Q = (1/(1-x) +1) / (x-2) (1 + 1 - x )/ [(1-x)(x-2)] = (x-2) / (x^2...
*January 14, 2016*