Wednesday

November 25, 2015
Total # Posts: 35,778

**Math**

|n| is just the distance from n to zero. n can be to the left of 0 or to the right of 0. |-3| = 3 because -3 is 3 units away from zero. -3 is to the left of 0, +3 is to the right, but in either case. |-3| = |+3| = 3 Get out your number line and try plotting some points. And ...
*October 5, 2015*

**Math; PLEASE CHECK MY ANSWERS**

1C 2D ok 3 B and C are both greater. Typo? If you meant 5.5x10^7, then just B
*October 5, 2015*

**math, mechanics**

Well, if F is dU/dr, and U is a function of r, then there will certainly be r in the answer. But, you want F(r) at r=r0, so geez, just plug in r0! Am/r0^(m+1) - Bn/r0^(n+1) There are other ways of expressing that, but that's another exercise.
*October 5, 2015*

**math, mechanics**

still looking for what F is.
*October 5, 2015*

**History**

thank you
*October 5, 2015*

**History**

I think a
*October 5, 2015*

**History**

What is a key element of democracy? a- self-determination b- selfishness c- violent d- heredity My answer would be a or b
*October 5, 2015*

**math**

either (7/5 * 60) or (7/2 * 60) depending on who got the $60.
*October 5, 2015*

**Language Arts (- Ribbons -)**

∫C (2z-3)/[(z^2-4)(z+2)] dz
*October 5, 2015*

**Math**

this keeps cropping up. See the related questions below. But, just follow the rules you have learned: -12 / 3 * (-8 + (-4)^2 - 6 ) + 2 -12 / 3 * (-8 + 16 - 6 ) + 2 -12/3 * 2 + 2 -4 * 2 + 2 -8 + 2 -6
*October 5, 2015*

**Math**

since 3/4 * 1 = 3/4 3/4 * 4/3 = 1 multiplying 3/4 by any number between 1 and 4/3 will work. Or, a little more formally, 3/4 <= (3/4) x <= 1 1 <= x <= 4/3
*October 5, 2015*

**Math help**

If there are x bargain boxes and y deluxe boxes, you want to maximize p = 4x + 6y where 4x+9y <= 300 8x+3y <= 400 Now use your favorite solution method or tool, and you find max p when x=45 y=13 http://www.zweigmedia.com/RealWorld/LPGrapher/lpg.html is a nice tool. It ...
*October 5, 2015*

**Geometry**

reflection through the line y=x moves (x,y) -> (y,x) So, it looks like C with a typo. I mean, geez, did you try actually plotting a point and seeing what happened if you flipped it over the line y=x? or maybe googling reflections? http://www.regentsprep.org/regents/math/...
*October 5, 2015*

**MATH 115 PRE-ALGEBRA**

Just use the distributive property to get rid of the parentheses: 6(3m-7)-2(12y-5)+4(y+6) 6(3m)-6(7)-2(12y)-2(-5)+4(y)+4(6) 18m-42-24y+10+4y+24 Now you can use the commutative property to rearrange things: 18m-24y+4y-42+10+24 18m+y(-24+4)-8 18m-20y-8 If that m was really ...
*October 5, 2015*

**Math**

well, 2007 is 1990+17, so just plug in 17 for t.
*October 5, 2015*

**calculus**

well, you only have two points, so a line would suffice to join them. But, as the slope at the end of the ramp is not 90/120, that gives another constraint. That's like specifying a third point. So, use a quadratic to model the ramp. y = ax^2+bx+c y(0) = 100, so c=100 y(...
*October 5, 2015*

**maths**

how many cards? how many aces of hearts? so, P(A♥) = ...
*October 5, 2015*

**Algebra**

well, your equation, which is already in standard form, just needs a value for b. just plug in a point x-2y=b 4-2(-2) = b so, b=8 x-2y=8 which is standard form with a=1 b=-2 c=8
*October 5, 2015*

**Math**

think about it. The y-axis has equation x=0 so, any line parallel to the y-axis, say, c units away, will have the equation x = c Your point is (4,5), so the line you want is x = 4 Its slope is undefined, since x never changes. The line is vertical.
*October 5, 2015*

**trigonometry**

If you drop an altitude from C to AB, call it P, and if AP=x then BP = 125-x. Then the river's width is CP. Call that w. We then have w cotA + w cotB = 125 w = 125/(cotA+cotB) Now just plug in your values for A and B.
*October 4, 2015*

**Math**

I think A,C,D are all needed.
*October 4, 2015*

**math**

I don't believe that c(x) is correct as stated. It means that c(x) increases with time, not likely for a cooling piece of metal. So, either c(x) does not represent the metal's temperature after x hours, or it indicates how many degrees it has cooled. In either case, c(...
*October 4, 2015*

**Physics**

well, the vertical position (in meters) of the spider at time t is y(t) = 0.890 sin 36° t - 4.9t^2 = 0.523t - 4.9t^2 So, what is y(0.0660)?
*October 4, 2015*

**Physics**

well, the vertical position at time t is y(t) = 20 sin40° t - 4.9t^2 = 12.86t - 4.9t^2 I think that should get you started ok.
*October 4, 2015*

**Calculus**

what are we to make of L4?
*October 4, 2015*

**math221**

I'm not so sure on those examples. They are all discrete events. How about continuous versions, such as the water depth during a flood how long you are likely to sleep the temperature of fevers during family illnesses
*October 4, 2015*

**Math**

x must divide 1400, which is 2*7*2*5*2*5 Can you make a guess now?
*October 4, 2015*

**Pre-Calculus**

Assuming the "rightmost edge" of a circle is the end of the horizontal diameter, we have hole is at H:(0,0) ball is at B:(-40,-50) ball exits at P:(35,0) So, the line joining B and P is y+50 = 2/3 (x+40) The circle is represented by x^2+y^2 = 35^2 The line intersects...
*October 4, 2015*

**Math**

well, (4x10)x10 = 4x(10x10)
*October 4, 2015*

**algebra**

what's all this power stuff? 1st piece = x 2nd piece = 2x 3rd piece = 4x So, you have x+2x+4x = 28 x = 4
*October 4, 2015*

**zambia school**

you know that PV/T is constant. So, you want P where (100)(500)/(293.15) = P(22400)/(273.15)
*October 4, 2015*

**Calculus**

so, what's the trouble? You have critical numbers where f'=0. But, as you found out, f' is never zero. So, ... there are no critical numbers. There is no place where the tangent line is horizontal. Just look at the graph and sigh: http://www.wolframalpha.com/input...
*October 4, 2015*

**algebra**

since √u is defined only for u >=0, your domain here is x-2 >= 0 x >= 2 SO, the point (2,0) is the left-most point. Now plot a few more points.
*October 4, 2015*

**algebra**

can you graph the line y=4? And also y=1? If so, graph both lines, then erase the parts for the excluded domains. What's left is the graph of f. Oh, and work on your typing and prooofreading, while you're at it.
*October 4, 2015*

**math**

well, just plug in the numbers! -x+4y = -(-4/5)+4(1/3) = 4/5 + 4/3 ... I assume that since you are apparently taking algebra, you can handle the fractions, no?
*October 4, 2015*

**math**

S = dF/dr So, what's F? If you mean dU/dr, then that would be Am/r^(m+1) - Bn/r^(n+1)
*October 4, 2015*

**math**

clearly, after t hours, the population is 2^t. So, when is 2^t = 3?
*October 4, 2015*

**Algebra**

sides are 4x,x,x perimeter is 6x the desired ratio is x/6x = 1/6
*October 4, 2015*

**calculus**

ever heard of the product rule? f = 5e^x cosx f' = 5e^x cosx - 5e^x sinx = 5e^x (cosx - sinx) f" = 5e^x (cosx - sinx) + 5e^x(-sinx-cosx) = -10e^x sinx
*October 4, 2015*

** Chem**

copper sulfate reacts with sodium hydroxide producing copper hydroxide and sodium sulfate.. If sodium hydroxide is the limiting agent how many grams of copper hydroxide should precipitate out?{There are 634.44 g of copper sulfate and 240 grams of sodium hydroxide.
*October 3, 2015*

**college algebra math help**

just use the quadratic formula, as usual.
*October 3, 2015*

**Math**

right on.
*October 3, 2015*

**calculus i need help also**

assuming you meant y = 2x^3-21x^2+60x+6 y' = 6x^2-42x+60 y" = 12x-42 y"=0 when x = 7/2 For the other one, (x^1/2+x^1/3)dx = 0 ∫(x^1/2+x^1/3)dx = C 2/3 x^(3/2) + 3/4 x^(4/3) = C at x=1, C = 2/3 + 3/4 = 17/12
*October 3, 2015*

**calculus need help**

not even sure what a "differencial coefficient" is Do you mean to find the derivative, using the definition as a limit?
*October 3, 2015*

**Algebra**

using the two-point form, we have y-1 = (-3-1)/(9+3) (x+3) Now simplify and put into standard form.
*October 3, 2015*

**Chemistry**

copper sulfate reacts with sodium hydroxide producing copper hydroxide and sodium sulfate.. If sodium hydroxide is the limiting agent how many grams of copper hydroxide should precipitate out?
*October 3, 2015*

**Calculus**

C(R) = .20R C(x) = .20(70x) The notation shown is confusing, since x is used for two different things.
*October 3, 2015*

**science**

position is measured in meters. Its change in time is velocity, m/s velocity's change in time is acceleration: (m/s)/s = m/s^2
*October 3, 2015*

**science**

well, since p = mv, just do the math...
*October 3, 2015*

**Integration need help also**

To make things a bit clearer, ∫sin(x^2) x dx let u = x^2 du = 2x dx and you have ∫1/2 sin(u) du not so hard, eh?
*October 3, 2015*

**@Reiny**

That's my favorite theorem! Too bad it's not taught more. In all fairness, when you're brand new at this stuff, things often seem more confusing than they are. The main problem I encounter is that students seem to forget what the exercise set covers. If you've ...
*October 3, 2015*

**Maths**

look at the remainders when dividing powers of 2 by 13: n 2^n mod13 0 1 1 1 2 2 2 4 4 3 8 8 4 16 3 5 32 6 6 64 12 7 128 11 8 256 9 9 512 5 10 1024 10 11 2048 7 12 4096 1 ... so, you see that 2^n mod 13 = 2^(n+12) mod 13 2011 = 167*12 + 7 so, 2^2011 mod 13 = 2^7 mod 13 = 11
*October 3, 2015*

**Physics**

ever see a 5-12-13 right triangle?
*October 3, 2015*

**Maths**

If the smaller plot has width w, then w*7w = 1250/5 7w^2 = 250 w = 5.976 so, its perimeter is 2(w+7w) = 95.6
*October 2, 2015*

**Math**

(-2√2,0) Just graph the point. See that it is at the end of the diagonal of a square. Now rotate it.
*October 2, 2015*

**Geometry**

Check the related questions below. If they don't do the trick, come back with further details on why not.
*October 2, 2015*

**math**

10x = 32.222222... x = 3.2222222... subtract and you have 9x = 29 x = 29/9 Similarly, 4.(3) = 4 1/3 = 37/9 So, (29/9):(37/9) = 29:37
*October 2, 2015*

**math help**

"dash"?? Oh, please. Surely you can write y-axis! However, your answer is correct. Or, would be had you written (-5,3).
*October 2, 2015*

**science**

relative to what?
*October 2, 2015*

**Math OMG Please help**

clearly, the height at x=0 is 45. So, y = 45 - (3/31)x The x-intercept, naturally, is how far away from the platform the ramp's height is zero.
*October 2, 2015*

**Alegbra PLEASE HELP**

all right! geez, wait for a respone before posting it all over again.
*October 2, 2015*

**Alegbra**

while A and C both produce the same value, A is clearly the best choice, since it shows (-7) multiplied 5 times.
*October 2, 2015*

**I need help maths jus so confused**

this has no algebraic solution. You need some kind of graphical solution. Take a look at the graph of x^x - 100 = 0 and you will see that x ≈ 3.6 http://www.wolframalpha.com/input/?i=x^x-100+for+3%3Cx%3C4 That is reasonable, since 3^3 = 27 4^4 = 256
*October 2, 2015*

**Alegbra**

so do I.
*October 2, 2015*

**Geometry**

not bad, except that you did not follow instructions: To the nearest whole number Oh, that and the fact that 2π * 7 * 45 = 1979.2 You apparently approximated π by 3.14
*October 2, 2015*

**Geometry**

Looks good, except the h=45, not 14
*October 2, 2015*

**Math/Algebra**

ummm, no. #1 (y√4)/(4*2) = (28√9)/(2*7) 2y/8 = 84/14 y = 84*4/14 = 24 #2 ok
*October 2, 2015*

**Math/Algebra**

y = kab/√c So, (y√c)/ab = k is constant. so, you want (y√4)/(4*2) = (28√9)/(2*7) Now just find y. y=kx/z^2 so, you want (y*25)/50 = (24*9)/27
*October 2, 2015*

**Math**

earth's circle is (x+4)^2 + (y+3)^2 = 60^2 So, the orbit is (x+4)^2 + (y+3)^2 = 60.4^2
*October 2, 2015*

**physics**

100Hz = 100cycles/s = 0.1cycle/ms 0.1cycle/ms * 80ms = 8 cycles
*October 2, 2015*

**math**

GCF(18,20) = 2. So, at most 2 groups can be made.
*October 2, 2015*

**MATH**

so, what is the shortest side? Then find its midpoint. Just use the distance formula, and recall that the midpoint's coordinates are the average of the endpoints' coordinates.
*October 2, 2015*

**Business Math**

#1 (679.99-599.99)/679.99 = 0.1176 or about 12% #2 (15-12)/12 = 25% #3 extra revenue during that week was 15*599.99 - 12*679.99 = 839.97 So, ...
*October 2, 2015*

**physics**

well, in t seconds it falls 4.9t^2 meters. Looks like t≈1
*October 2, 2015*

**Calculus 1**

well, just do it normally: y' = 1/(9x^2+7y^2) * (18x+14yy') Now just factor out the y' stuff. Or, rewrite as e^y = 9x^2 + 7y^2 e^y y' = 18x + 14yy' y' = 18x/(e^y-14y) = 18x/(9x^2+7y^2-14y)
*October 2, 2015*

**Calculus 1**

y(x) = (9lnx)/x y'(x) = 9(1-lnx)/x^2 y'(1) = 9 y'(e) = 0 Now just use the point-slope form of the lines.
*October 2, 2015*

**Foley**

angle 1 + angle 2 = 90° But I'm sure Maddie caught that...
*October 2, 2015*

**Math**

well, they all add up to 360, so ...
*October 2, 2015*

**math**

you have it exactly backwards. To find out how many times 2 divides 10, you divide 10/2, not 2/10. So, 16.3/0.1 = 163
*October 2, 2015*

**physics**

E is in kg-m^2/s^2 p is in kg/m^3 A is in m^2 g is in m/s^2 So, we have kg-m^2/s^2 = kg^2/m^6 m^2/s^4 m^2 C kg-m^2/s^2 = kg^2/m^2-s^4 C C = (kg-m^2/s^2)(m^2-s^4/kg^2) = m^2-s^2/kg
*October 2, 2015*

**Maths**

(x-√2)(x+√2) = x^2-2 (2x^4+7x^3-19x^2-14x+30)/(x^2-2) = 2x^2+7x-15 Now you can factor that to find the other two roots
*October 2, 2015*

**Find x and y and also log**

2^x+y = 6 3^x-y = 4 6-2^x = 3^x-4 2^x+3^x = 10 A graphical solution is probably the best bet here. a^2+b^2=7ab a^2+2ab+b^2 = 9ab (a+b)^2 = 9ab 2log(a+b) = log 9ab log(a+b) = log(9ab)/2 = log√9ab = log√9 + log√ab = log3 + log(ab)/2 = log3 + (loga+logb)/2
*October 2, 2015*

**Math**

Does (0.025 + 1/2x) occur twice? It's hard to tell. If it does, and multiplies as written, then you just have 1.7 x 10^-3 = (0.0015 - x)^2 0.0015 - x = ±0.041 and that you can handle.
*October 2, 2015*

**Maths**

f(x) = x^2+8x-6 if the roots are 1/2 as much, then they are the roots of f(2x) = 4x^2+16x-6 I'll let you check with the quadratic formula.
*October 2, 2015*

**College Algebra**

clearly you are intended to use the Rational Zeroes Theorem, and start guessing. A little synthetic division reveals that there are no rational roots at all. So, the only possible roots will involve cube roots, and be very hard to find. I suggest graphing it and approximating ...
*October 2, 2015*

**Spanish**

Hi Sra! Could you please check my answers on these questions? 1) -Como quiera. Mientras Ud. ______ un sobre, yo limpiaré el compartimento. (MIRAR / BUSCAR) - Busque 2) Pero, por favor, antes de que Ud. se ________, (IR / VER) - Vayas 3) Cuando llegues (8) _____, ven (9...
*October 1, 2015*

**Math**

if it's air speed is 267 ft/s, then its vertical speed is 267 sin 16° = 73.595 ft/s So, to gain an altitude of 12500 ft takes 12500/73.595 = 169.848 seconds, or 2.83 minutes
*October 1, 2015*

**algebra**

the fraction left after d days is 0.5^(d/140) So, after 1 day, that is 0.99506 for a daily decay rate of 0.494% Now just plug in d=425
*October 1, 2015*

**Pre-calculus**

correct.
*October 1, 2015*

**Maths**

since it's a cubic, it's hard to do without calculus. The easiest way is to examine its graph. http://www.wolframalpha.com/input/?i=0.2t%28t-5.1%29%28t-9.1%29 Looks like t≈2.1 or 7.4
*October 1, 2015*

**Sequences and Series**

ahem. what is 25-3*8? minus, not plus.
*October 1, 2015*

**please help!!**

Assuming you meant f = (2x-6)/(x+1) using the quotient rule, f' = [(2)(x+1)-(2x-6)(1)]/(x+1)^2 so, at x=0, f' = (2+6)/2 = 4 Or, you can note that f = (2x-6)/(x+1) = 2 - 8/(x+1) so, f' = 8/(x+1)^2 f'(0) = 8/2 = 4
*October 1, 2015*

**math**

clearly it is 4160/x
*October 1, 2015*

**Math - eh?**

Try proofreading your posts.
*October 1, 2015*

**astronomy**

1 Watt = 1 J/s = 10^7 erg/s 1GW = 10^9 J/s the area of the sun is 4pi*(7*10^5 km)^2 = 6.2*10^12 km^2 So the solar output is 4*10^17 GW/6.2*10^12km^2 = 6.452*10^4 GW/km^2 So, now the question is: how much of that reaches the earth? I guess you need to use the inverse-square law...
*October 1, 2015*

**astronomy**

1/2 " = 2.424*10^-6 radians So, find r using s = rθ
*October 1, 2015*

**math?**

Not A: The contrapositive of X is if you don't raise your heart rate, you did not run for 10 min.
*October 1, 2015*

**AP Calculus**

if the rectangle is x wide by y high, then the diameter of the window is x. So x + 2y + π/2 x = 72 thus, y = [72-(1 + π/2)x]/2 The area is a = xy + π/8 x^2 = x[72-(1 + π/2)x]/2 + π/8 x^2 = 36x - (1+π/4)x^2 + π/8 x^2 = 36x - (1 + 3π/8)x^2...
*October 1, 2015*

**Help!! Geometric progression**

r=2, so you want a(2^(2n)-1) = 33a(2^n-1) n=5 ar * ar^3 = 2ar^4 a(r^4-1)/(r-1) = 80 a=2, r=3 GP: 2,6,18,54,162
*October 1, 2015*