Tuesday

January 17, 2017
Total # Posts: 47,908

**Science**

recall that F = ma

*December 14, 2016*

**math**

what's to justify? It has a steepness...

*December 14, 2016*

**Algebra**

clearly, at x = -2 and 1.

*December 14, 2016*

**Math**

11th term is a+10d that will make a difference.

*December 14, 2016*

**Math**

try putting things into standard form: (2x+6)(3x-1)=2 6x^2 + 16x - 6 = 2 6x^2 + 16x - 8 = 0 or 3x^2 + 8x - 4 = 0 Now just use the quadratic formula.

*December 14, 2016*

**algebra**

it already is. Just add the power of 10 3.000052 * 10^0 Now, if you mean that problem #3 was .000052, that is 5.2 * 10^-5

*December 14, 2016*

**Math**

why use 50 for the common denominator, when 10 works just as well? 13/5 + 29/10 = 26/10 + 29/10 = 55/10 Now subtract that total from the 11 hours (110/10) needed, and you still need 55/10 = 5 1/2 275/50 is 5 1/2, not 5/2.

*December 14, 2016*

**algebra**

moving the decimal point 6 places to the right, we get 6.98 * 10^-6

*December 14, 2016*

**Math**

(1+r)^4 = 1.75

*December 14, 2016*

**Math**

How about some parentheses? Just guessing here, I read e^(4x-3) = 2e^(2x) No idea what the final 1 is. Anyway, I'll work this, and then you can fix it if necessary. Taking logs of both sides, we get 4x-3 = ln2 + 2x 2x = 3+ln2 x = (3+ln2)/2 ln(2x+6) - ln(3x-1) = ln(2) (2x+6...

*December 14, 2016*

**Math**

when 1.026^x = 3

*December 14, 2016*

**pre calc**

so, list the values for x calculate and list the values of y. Something hard about that?

*December 14, 2016*

**Math**

A is decreasing when A' < 0 The growth rate G' is maximal when its derivative (G") is zero. Just as G has a max when G' = 0.

*December 14, 2016*

**math**

depends on how many grades you already have. The more low grades you have for the 76% average, the higher grade you will need to raise it to 81%.

*December 14, 2016*

**Business Math**

revenue = price * demand Assuming the usual carelessness with parentheses, r(x) = x*p(x) = x(50/(0.01x^2 + 1)) The maximum revenue is found at x=10. See the graph and other info at http://www.wolframalpha.com/input/?i=x(50%2F(0.01x%5E2+%2B+1))

*December 14, 2016*

**precalculus**

The 2nd difference is not 1 (7-6). The 2nd difference is the sequence of differences of the 1st differences. You have sequence: 7, 6, 7, 10, 15, 22,... 1st diff: -1,1,3,5,7,... 2nd diff: 2,2,2,2,... 2nd ok 3rd. Did you actually try your formula? (Assuming you meant 21.5x) y(1...

*December 14, 2016*

**precalculus**

#1 If you meant Pk=2^(k-1)/k! then Pk+1 = 2^k/(k+1)! #2 If Pk = 7 + 13 + 19 + ...+[6(k - 1)+1] + (6k + 1) Pk+1 = 7+13+...+(6k+1)+(6(k+1)+1) = 7+13+...+(6k+1)+(6k+7) #3 The first step is to show that P(1) is true #4 You assume that 3 + 11 + 19 + 27 + … + (8n - 5) = n(4n - ...

*December 14, 2016*

**MATH FOR LIBERAL ARTS**

well, 1 in = 2.54 cm so just multiply the height (in inches) by 2.54

*December 14, 2016*

**precalculus**

come on -- just plug in k+1 for k: Pk+1 = (2(k+1)-1)/(k+1)! = (2k+1)/(k+1)!

*December 14, 2016*

**precalculus**

the differences are 0,2,4,6,8,... Tn+1 = Tn + 2(n-1) so, Tn = n^2-3n+5

*December 14, 2016*

**precalculus**

I assume you mean n! > 2^n 4! > 2^4 for n>4, n! = 4!*5*6*...*n > 2^4*2*2*2...*2

*December 14, 2016*

**Maths**

The set 1 2 5 7 10 has mean=5 median=5 Now, if you don't want integers, then fudge the values a bit. 1.1 2.1 5 6.9 9.9 The mean is still 5. Since there are an odd number of values, the median must be the center number. If it is 5, then the median is an integer. I see no ...

*December 14, 2016*

**Calc 2 Urgent Surface Area of Revolution Question**

You can do that too.

*December 14, 2016*

**Calc 2 Urgent Surface Area**

Oh yeah. Sorry I did the volume instead. Consider the surface as a pile of circular rings, each with circumference 2?r. So, the surface area is S = ?[0,1] 2?x ds but ds is a small piece of the line, of length ds^2 = dx^2+dy^2 = dx^2 + (4dx)^2 = 5dx^2 S = ?[0,1] 2?x?5 dx = ?5...

*December 14, 2016*

**math**

a fraction of what? a kg? a ton? an ounce?

*December 14, 2016*

**Math**

Is this some kind of truncated triangular pyramid? Your description is a bit vague.

*December 14, 2016*

**precalculus**

same as the others. pick values for ?, figure x and y, then just plot the points! Note that since cos^2?+sin^2?=1, ((x-2)/3)^2 + (y/2)^2 = 1 Looks like an ellipse to me.

*December 14, 2016*

**precalculus**

you can either (a) find and fix my typo (b) read bobpursley's solution, which is correct.

*December 14, 2016*

**precalculus**

just like the other one! pick some values for t, calculate x and y, and plot the points. First, decide whether you meant x=?(t^2+2) or x=?t^2 + 2) I suspect the former, since ?t^2 = |t| So, x is basically just t y is basically just t. The graph will be almost a straight line ...

*December 14, 2016*

**precalculus**

No. x = 2 + 3cos? NOT x = (2+3)cos?

*December 14, 2016*

**intermediate algebra**

you have the equations. Now just solve them.

*December 14, 2016*

**Calc 2**

No calculus need for this one. It's just a cylinder with a cone cut out. r=1 h=4 v = ?r^2h - ?/3 r^2h = 2?/3 r^2h = 8?/3 Ok ok. If you want to use calculus, then with shells, v = ?[0,1] 2?rh dx where r=x and h=y=4x v = ?[0,1] 2?x*4x dx = 8?/3 using discs (washers) you get ...

*December 14, 2016*

**precalculus**

no idea. It's a set of parametric equations. You can use pi as a value if you wish.

*December 14, 2016*

**precalculus**

no idea. What does pi have to do with it?

*December 14, 2016*

**precalculus**

pick some values for t, calculate x and y, and plot the points. Nothing hard about that. You can tell it will be a parabola, since you already figured out that x = (2y+2)^2 - 6

*December 14, 2016*

**Algebraic equations real life problems**

You have your two equations. 3b = 2+a 3a-b = 2+a+2b rearrange things a bit and you have a - 3b = -2 2a - 3b = 2 subtract and you have a=4 so, b=2

*December 14, 2016*

**Algebraic equations real life problems**

as you know, perimeter is 2(length+width) With no actual numbers provided, it is impossible to assign values to a and b.

*December 14, 2016*

**Math**

9/12 - 8/12 = ?

*December 14, 2016*

**Calculus**

v = x^2y 4x+y <= 6 see where that takes you.

*December 14, 2016*

**maths**

given the murky question, 36 seems as good an answer as any...

*December 14, 2016*

**physics**

face north turn eastward (clockwise) 28 degrees. Now you are facing N28°E

*December 14, 2016*

**Math help please I do not understand it**

7 3/5 what? feet? meters? inches?

*December 14, 2016*

**OBJECT ORIENTED PROGRAMMING**

you expect someone here to undertake such a project and do it all for you? Don't ask much, do you?

*December 14, 2016*

**Math**

can't spell, either, eh?

*December 14, 2016*

**math**

x + x+1 + x+2 = 126 ...

*December 14, 2016*

**math**

yes. send your check to me and I'll email them to you.

*December 13, 2016*

**math**

I predict that it was a bottle of nail polish.

*December 13, 2016*

**gms**

post the file online, rather than expecting us to access it on your computer...

*December 13, 2016*

**Algebra**

x^2/25 + y^2/100 = 1 the major axis is vertical. a = 10 b = 5 c^2 = a^2-b^2 = 75 The foci are at (0,±c)

*December 13, 2016*

**Math**

I'll do the x's. You can then use the steps for the t's: 4(3x - 1)= 3 + 8x - 11 12x-4 = 8x-8 4x = -4 x = -1

*December 13, 2016*

**Math**

3C2 = 3

*December 13, 2016*

**math**

12/3 = 4 lockers So, 4/3 cans for 4 lockers ... -(-0.45) ...

*December 13, 2016*

**Math**

remember these? http://www.sosmath.com/trig/prodform/prodform.html

*December 13, 2016*

**maths**

If you meant (11-w)/4 = 1-w 11-w = 4-4w 3w = -7 w = -7/3 If you meant 11 - w/4 = 1-w 3w/4 = -10 w = -40/3

*December 13, 2016*

**Math Percents: Please help!!**

nope. 240 * 1.15 = 276 264 is a 10% increase: 240+24

*December 13, 2016*

**Algebra**

well, the elements must match, so -3x = 12 7 = 7 2y = x+y I think that you can take it from there, yes?

*December 13, 2016*

**Math Help**

(g?f) = g(f) = 9f+3 = 9((x-3)/(x9))+3 And you can massage that as you like (whatever x9 means...)

*December 13, 2016*

**Trig Question**

If you meant 6cos(3?)/2+3=0 that is just 3cos3? + 3 = 0 cos3? = -1 3? = ? ? = ?/3 The period is 2?/3, so ? = ?/3 + k(2?/3) = ?/3, ?, 5?/3 see the graph at http://www.wolframalpha.com/input/?i=plot+6cos(3%CE%B8)%2F2%2B3%3D0,+0+%3C%3D+%CE%B8+%3C+2pi Now, if you meant 6cos(3?/2)+...

*December 13, 2016*

**precalculus**

Huh? Use your numbers: cot2? = (1-1)/6 = 0 2? = 90° ? = 45° http://www.wolframalpha.com/input/?i=x%5E2%2B6xy%2By%5E2-6%3D0

*December 13, 2016*

**precalculus**

tan2? = B/(A-C)

*December 13, 2016*

**precalculus**

come on. just substitute it into the other equation. t = 2y+2 x = t^2-6 = (2y+2)^2-6 = ... It is clearly a horizontal parabola

*December 13, 2016*

**precalculus**

well, t = 2y+2, so use that

*December 13, 2016*

**precalculus**

well, |cos3?| <= 1 cos3?=0 when 3? is an odd multiple of ?/2

*December 13, 2016*

**precalculus**

the ellipse looks good, but y=-t^2 x=-t^2+4 becomes x-y=4 not x-y^2 = 4 same for t^3

*December 13, 2016*

**Pre-algebra PLease help**

I get: 1C 2B 3C (2/3 is just 2 * 1/3) 4A 5A 12 is 50% of 24 That is a good first estimate. However, you are correct that 11 is closer (.48*23.95 = 11.49). I would have guessed 12, but 48% is a bit less than 50%, and 23.95 is a bit less than 24, so my estimate was a bit high. ...

*December 13, 2016*

**chemistry**

how many moles of SiO2? Each mole needs 3 moles of C. similarly for the other parts. work with moles, then back to grams.

*December 13, 2016*

**ALGEBRA 2**

g(x) = f(x-8)-7

*December 13, 2016*

**algebra**

ummm ... h?

*December 13, 2016*

**math**

cosx/(secx-tanx) = cosx / (1/cosx - sinx/cosx) = cosx / (1-sinx)/cosx = cos^2x / (1-sinx) = (1-sin^2x)/(1-sinx) = (1+sinx)(1-sinx)/(1-sinx) = 1+sinx why the word "plus"? You have a missing + key?

*December 13, 2016*

**precalculus**

Hmmm. The standard form for the polar conics is r = ep/(1 + e sin?) While your equation looks correct, I'd have written it as r = (5/2) / (1 + (5/4) sin?) to make it clear what the parameters are. Or, if you dislike fractions, r = 10/(4+5sin?)

*December 13, 2016*

**Alegrebra 2**

horizontal axis or vertical? Where is the vertex or directrix? You need to give more information. Depending on the vertex, many parabolas have that focus.

*December 13, 2016*

**Math**

construct AB with length 4.8 find the midpoint M of AB with M as center, draw a circle P with radius 3.6 with B as center, draw a circle Q with radius 5.2 Where P intersects Q is C.

*December 13, 2016*

**precalculus**

the rotation angle ? is such that tan2? = B/(A-C)

*December 13, 2016*

**Math grade 6, two-part problem**

If the four had amounts w,x,y,z then we know that w+x+y+z = 60 w = (x+y+z)/2 x = 2/3 (y+z) y = 3z w,x,y,z = 20,16,18,6 Amy = w = 20 Nick-Cal = x-z = 16-6 = 10

*December 13, 2016*

**precalculus**

after all the similar exercises we have done, you still have no work of your own to show?

*December 13, 2016*

**Math**

no, the empty box is there so you can subtract it and see how much was crackers, not "tare weight" as it is called.

*December 13, 2016*

**Math**

the mass of crackers in one box is p-0.2 kg so, multiply that by 5 and you get 5p-1 kg So if you got several results, why did you not bother to show how you arrived at each? Maybe one of them was right!

*December 13, 2016*

**mathes for management**

enter your data at this site for all the details: http://www.gregthatcher.com/Mathematics/GaussJordan.aspx

*December 13, 2016*

**Calculus AB**

what you want is the moment when the particle changes direction. That is, when v(t) = 0. t=2 is the first such time, so you just want s(2) = 55 a(2) = -18 Makes sense, since the velocity is changing from + to -, that the acceleration would be negative. If you want the values ...

*December 13, 2016*

**Algebra**

the slope of AC is -1/3 Thus the line AC is y-2 = -1/3 (x+3) The diagonals are perpendicular bisectors. The midpoint of AC is (3,0). The slope of BD is 3, so the line BD is y-0 = 3(x-3) Note that you don't need the other vertices B and D.

*December 13, 2016*

**physics**

<0,4> + <3.46,-2> = <3.46,2> = 4N 30 degrees above the x-axis. Makes sense. Since the two vectors are the same magnitude, and 120 degrees apart, their resultant will be 60 degrees from each.

*December 13, 2016*

**Math**

the outside diameter d = 2.5/3.14 = 0.796 So, the inside diameter is 0.796-0.0625 = 0.734

*December 13, 2016*

**math**

100gal * 8.34lb/gal = 834 lb 100gal * 0.71kg/L * 2.2lb/kg * 3.78L/gal = 590 lb or, note that 1kg/L = 8.34lb/gal

*December 13, 2016*

**Math**

-3(x-5y)+1÷2 (4x-10y) assuming you mean -3(x-5y)+1 --------------- 2(4x-10y) that is (-3x+15y+1)/(8x-20y) Your syntax is a bit ambiguous. And where do you get off using the multiply operator (×) for a variable (x)? Seems a lot of trouble.

*December 12, 2016*

**h.p.**

your sum is n ? (3k-2)^2 = ?9k^2 - 12?k + ?4 k=1 ?k^2 = n(n+1)(2n+1)/6 ?k = n(n+1)/2 ?4 = 4n Add them up and you have 9n(n+1)(2n+1)/6 - 12n(n+1)/2 + 4n = n(6n^2-3n-1)/2

*December 12, 2016*

**math**

if we let t = ?x, we have t^2-6 = t t^2-t-6 = 0 (t-3)(t+2) = 0 t = 3 or -2 so, x = 81 or 16 But, since ?x is positive, only x=81 satisfies the original equation. So, the extraneous solution can arise even when the original equation is not squared. Trying to use x=16 gives us ?...

*December 12, 2016*

**Math**

3/10 * 5/10

*December 12, 2016*

**reading and preschoolers**

I don't know what the prevailing educational theory is, but the best thing you can do to help your kids enjoy reading is to read to them. That way they learn to associate reading with enjoyable experiences, and they will want to keep on reading even when story time is over...

*December 12, 2016*

**Math**

{-4,-3,-2}

*December 12, 2016*

**math**

10 - 6 = 4 4 + 10 = 14

*December 12, 2016*

**math**

land distance: x water distance: ?(1^2+(2-x)^2) Now determine the cost c(x) and find its minimum.

*December 12, 2016*

**math**

what platform? volume = area * height = 40h the well's volume is pi r^2 h = 56pi so, 40h = 56pi

*December 12, 2016*

**precalculus**

x = 4cos(t) y = 2sin(t) x^2+4y^2 = 16cos^2(t)+16sin^2(t) = 16

*December 12, 2016*

**Math**

again? What do you know about converses? p?q but what does that say about q?p ?

*December 12, 2016*

**math**

If you want to solve it, then let u=2/(x-2). Then you have u^2-3u+2=0 (u-2)(u-1) = 0 so, u=1 or u=2 Substitute that back for x and then you can find the solutions.

*December 12, 2016*

**Pre-Calculus**

think about it. (x+y)^n has + signs for all the terms. (x-y)^n has minus signs for all the odd powers of n, since that is the same as (x + (-y))^n I'm sure you can provide your own examples. You might also try this web site: http://www.wolframalpha.com/input/?i=(x-y)%5E5 ...

*December 12, 2016*

**h.p.**

time to do some thinking, using what you already know. Your sum is ?k(k+1)(2k+1) = 2k^3 + 3k^2 + k = 2?k^3 + 3?k^2 + ?k These are just special sums whose formulas you already know.

*December 12, 2016*

**math**

what do you mean by "completes"? The sequence goes on forever, as indicated by the ellipsis. And, you don't provide any choices anyway...

*December 12, 2016*

**math**

y:g = 15:3 = 5:1 = 35:7

*December 12, 2016*