Saturday

April 30, 2016
Total # Posts: 40,032

**calculus**

dp/dt = 2√(pt) dp/√p = 2√t dt 2√p = 4/3 t^(3/2) + c p = (2/3 t^(3/2) + c)^2 Now plug in t=1 to find c.
*March 20, 2016*

**Math**

Nope. This is an example of poor notation. What he means is -4(2x + 5)^2 but doesn't know how to write it. You'll see this often here. So, to expand that we have -4((2x)^2 + 2*2x*5 + 5^2) = -4(4x^2+20x+25) = -16x^2 - 80x - 100
*March 20, 2016*

**Math**

the area grows as the square of the linear scale. So the scale is √(160in^2/2250ft^2) = √(160/32400 in^2) = √(1/2025) = 1:45
*March 20, 2016*

**Math**

The short sides cannot be 7, because then you would have a base of 14, and a height of zero. (The two 7" sides would lie down flat on the base.) Remember that any side must be less than the sum of the other two sides. So, the base must be 7 and the two equal sides are 14...
*March 20, 2016*

**Math**

just pick values for x and calculate values for y. Same as for any relation. Take advantage of symmetry, and you can save half your work. x x^2 0 0 1 1 2 4 3 9 4 16 and the same values for x=-1,-2,-3,-4,... Now watch what happens for the next one. x (x-2)^2 2 0 3 1 4 4 5 9 6 ...
*March 20, 2016*

**Discrete Math Help**

#1 nC2 = n(n-1)/2 I think you have a typo. #2 N = 17C2 * 5C1 is the total number of ways he can pick a meal. But, he has each of 30 days to make a different choice. That means there are NC30 different meals he can make. If the order makes a difference (same meals on different ...
*March 20, 2016*

**logarithm help!!!!**

Okay, if that's what you want. But trying to understand logarithms without the basic algebra skills you need can be very confusing and frustrating. Still, different strokes for different folks. If you can piece it all together, you're a better man than I. When I was in...
*March 20, 2016*

**logarithm help!!!!**

I'm a little confused here. You are asking about logarithms, and yet in another post you ask the most basic Algebra I type questions. Are you trying to pick this up on your own, with no class? A noble endeavor to be sure, but it seems you might go about it more ...
*March 20, 2016*

**expansion help!!! maths**

I'll let you read up on trinomial expansions, and just refer you here: http://www.wolframalpha.com/input/?i=%281%2Bx-x^2%29^6 scroll down a bit to see the full expanded form. This web site is a good place to play around and explore various math topics, play around with ...
*March 20, 2016*

**Physics**

Draw a FBD of an object that has forces acting on it that are not at right angles. If someone can provide me of some sort of example of what situation could represent this i would appreciate it.
*March 20, 2016*

**physics**

Since it has constant velocity, there is no acceleration. So, it must have zero net force acting on it. So, figure the downward force due to gravity, and it must be experiencing the same upward force from friction.
*March 20, 2016*

**Math**

x/200 = cot 22.3°
*March 20, 2016*

**Math haha**

Or, since it is the difference of two squares, (7/2+5/6)^2 - (7/2-5/6)^2 = (7/2+5/6 + 7/2-5/6)(7/2+5/6 - 7/2-5/6) = (7)(5/3) = 35/3
*March 20, 2016*

**Math**

1 > x > 9/8 is not possible, since 1 < 9/8
*March 20, 2016*

**Math**

no idea. Start listing them. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ... Seems like kind of a dumb question.
*March 20, 2016*

**mathematics-Algebra**

just put the words into math: If the numbers are x and y, then sum: x+y difference: x-y avg of sum and difference: ((x+y)+(x-y))/2 = x diff of sum & diff: (x+y)-(x-y) = 2y product is thus 2xy=12 3x+y=11 even with no further algebra, it is easy to see that x=3 and y=2
*March 20, 2016*

**Math**

t+o=8 6t+7o=53
*March 20, 2016*

**Algebra**

8*10*L = 2080
*March 20, 2016*

**MATH**

right.
*March 20, 2016*

**Physics**

A 5kg block is being pulled on a horizontal frictionless surface. The tension in the string is 30N. What is the total work done on the block as it moves a distance of 10 meters? Thank you very much!
*March 20, 2016*

**math**

4:5
*March 20, 2016*

**math**

x = ky^3 1 = k*2^3 k = 1/8 now just crank out the answers
*March 20, 2016*

**Math - incomplete**

got to know the total number sold. All you've said is that s = 3h you still need s+h = ? Fill in that value and then solve the two equations.
*March 19, 2016*

**Calculus**

h=3r, so r = h/3 v = π/3 r^2 h = π/3 (h/3)^2 h = π/27 h^3 dv/dt = π/9 h^2 dh/dt So, plug in your numbers to get dh/dt.
*March 19, 2016*

**Calculus**

h=3r, so r = h/3 v = π/3 r^2 h = π/3 (h/3)^2 h = π/27 h^3 dv/dt = π/9 h^2 dh/dt So, plug in your numbers to get dh/dt.
*March 19, 2016*

**Math**

oops. 56.4% is $146,094.05
*March 19, 2016*

**Math**

multiply 259032 * 0.56 = $145,057.92 Looks like you have a lot of reviewing to do!
*March 19, 2016*

**Math**

the equity is the value less any debts. So, it is 367685-108653 = $259,032 Surely you can figure out 56.4% of that number.
*March 19, 2016*

**math**

is there a question here? I'm no golf expert, but it seems to me that I've always seen negative numbers as below par.
*March 19, 2016*

**math**

LCM(8,10) = 40
*March 19, 2016*

**math series - eh?**

You sure that last value is 1/12, and not 1/24?
*March 19, 2016*

**series**

3 = 1*3 8 = 2*4 15 = 3*5 You sure 1/12 is next? Not 1/24, since 24 = 4*6
*March 19, 2016*

**Calculus**

with height x mm, v = (750-2x)(300-2x)x = 4(x^3-525x^2+56250x) dv/dx = 12(x^2-350x+18750) dv/dx = 0 at x=175±25√19 now pick the one which provides a max, not a min.
*March 19, 2016*

**math**

(2+√7)(2-√7)+√7 4-7+√7 -3+√7 a = -3 b = -1
*March 19, 2016*

**integral calculus**

using shells, v = ∫[0,a] 2πrh dx where r = x and h=2y=4√(ax) v = ∫[0,a] 2πx(4√(ax)) dx = 16/5 πa^3 using discs, v = ∫[0,2a] π(R^2-r^2) dy where R=a and r=x=y^2/(4a) v = ∫[0,a] 2π(a^2-(y^2/(4a))^2) dy = 16/5 πa^3
*March 18, 2016*

**Calculus (Line Integral)**

oops: here is http://math.oregonstate.edu/home/programs/undergrad/CalculusQuestStudyGuides/vcalc/arc/arc.html#alfunction
*March 18, 2016*

**Calculus (Line Integral)**

Actually, just consider the definition of T. Take a peek here, and it should be clear, since the arc length is just ∫ ds = ∫ |dr/dt| dt
*March 18, 2016*

**Calculus (Line Integral)**

Hmmm. Let me dig out my text on differential geometry. Meantime, try googling the topic in vector analysis.
*March 18, 2016*

**Math/Precal**

well, cos(A-B) = cosAcosB + sinAsinB
*March 18, 2016*

**Precal/Math**

Hint: what is 1/(1+u) + 1/(1-u) as a single fraction?
*March 18, 2016*

**Mrs. Sue**

#3 using #2, (B) #4 A=πdh=125.6 so, (C) #5 lateral area is circumference * height = 2πrh
*March 18, 2016*

**Help ASAP**

if the radius is 7 cm, then the area is 4πr^2 = 4π*49 = 615.75 cm^2
*March 18, 2016*

**math help pls pls pls**

the y-intercept is the cost when x=0, or no hours worked. So, the correct answer is C
*March 18, 2016*

**Geometry**

#1: A = 4πr^2 = 4π*1^2 = 4π #2: correct, if the radius is 27cm.
*March 18, 2016*

**math**

well, just list them. If the points are A,B,C left-to-right, then you have 6 ways to pair them up: AB BA AC CA BC CB But the ray going right from A passes through both B and C, so AB and AC are the same ray. Similarly, CB and CA are the same ray. BA and BC point in opposite ...
*March 18, 2016*

**Math/precal**

19π/6 = 3π + π/6 The tan function has period π, so tan(19π/6) = tan(π/6) = 1/√3
*March 18, 2016*

**Math/Precal**

(1-tanx)/(1-cotx) (1-tanx)/(1 - 1/tanx) (1-tanx)/((tanx-1)/tanx) (1-tanx)(tanx) / (tanx-1) -tanx
*March 18, 2016*

**sgfrsargehw**

paha maia
*March 18, 2016*

**physics take 2**

s(t) = s0 + v0t + 1/2 at^2
*March 18, 2016*

**physics**

final speed = 0 easy. just apply s(t) = s0</sub + v0</subt + 1/2 at^2
*March 18, 2016*

**Geometry 5 questions**

#1 D #2 nope #3 nope #4 C #5 B Clearly you need to review these basic transformations. Reflection through the xy plane changes the sign of the z coordinate. xz: change y yz: change x for translations, just add the indicated amounts to the coordinates.
*March 18, 2016*

**Math ASAP**

both correct.
*March 18, 2016*

**Math HELP**

Looks good to me.
*March 18, 2016*

**MATHS**

If the price is p and the cost is c, then 15p = 20c p/c = 20/15 = 1.333 so, he made 33% profit
*March 18, 2016*

**MATH**

#1 B is the only possible candidate, assuming it never repeats #2 well, 150 is not a perfect square #3 do you know your 12 times tables? #4 have you a calculator? try taking the square root 625.
*March 18, 2016*

**1st grade math**

there are probably many online math games he can play. google is your friend.
*March 18, 2016*

**MAth**

well, 2 bundles per foot 3 feet per yard ...
*March 18, 2016*

**math**

150
*March 18, 2016*

**Integer math**

Your answers seem correct, but I fail to see the point of the first two. Find 7 ? answer = 7 ? well, duh. seems kind of bogus to me.
*March 18, 2016*

**math**

23 + 5 × 10 ÷ 2 – 33 + (11 – 8) 23 + 5 × 10 ÷ 2 – 33 + 3 23 + 50 ÷ 2 - 33 + 3 23 + 25 - 33 + 3 48 - 33 + 3 15 + 3 18
*March 18, 2016*

**geography**

diagonal is √(2^2 + 3^2 + 5^2) = √38
*March 18, 2016*

**mathematics-state of rules**

Do you know what the rule is? If not, read http://mathworld.wolfram.com/OsbornesRule.html and the identity is easy to adjust.
*March 18, 2016*

**mathematics-evaluation**

no idea what that means. Do you want the first 5 terms of the power series? e^x = 1 + x + x^2/2! + x^3/3! + x^4/4! + ...
*March 18, 2016*

**Maths**

sin^2 = 1-cos^2, so 4 + 4cos = 1 - cos^2 cos^2 + 4cos + 3 = 0 (cosx + 1)(cosx + 3) = 0 cosx = -1 or -3 -3 is out, so cosx = -1. x = 180 or -180 2sinx = 5cosx tanx = 2/5 x ≈ 21.8° tanx is positive in QI and QIII, so our solutions are x = 21.8° or -158.2°
*March 18, 2016*

**surface area and volume**

how much soil. "many" is used to count individual items, and "much" is used to measure a quantity such as volume. Recall that the volume of a cylinder of radius r and height h is v = π r^2 h Now just plug in your numbers. Volume is in units of m^3.
*March 18, 2016*

**Maths**

These are just quadratic equations. You can factor them as follows: (tanx + 4)(tanx - 1) = 0 (2sinx + 1)(sinx - 1) = 0 Now they are easy, right?
*March 18, 2016*

**Math**

y = x^3-7
*March 18, 2016*

**math**

half a building with 46 is 23. So, 8+B = 2+23
*March 18, 2016*

**another integral...help**

Not sure how to interpret tan^-1/(1+x^2)^2 You don't seem to have a numerator for the fraction. One way, which provides the easiest integration is ∫ x [tan(1+x^2)]^2 dx Let u = 1+x^2 du = 2x dx and you have 1/2 ∫ tan^2(u) du = 1/2 ∫ (sec^2(u) -1) du = 1/2...
*March 18, 2016*

**integration i need**

just expand and divide each term by e^4x. That gives 1/e^4x - 5/e^3x + 10/e^2x - 10/e^x + 5 - e^x That's easy to integrate, recalling that ∫ e^ax dx = 1/a e^ax
*March 18, 2016*

**geometry**

Draw a diagram. Let P be the point where it turned. If it turned θ north of west, then the interior angle at P is 180-θ. Then, by the law of cosines, remembering that cos(180-θ) = -cos(θ), 83^2 + 111^2 + 2*83*111 cosθ = 165^2 Now just solve for θ.
*March 18, 2016*

**geometry**

Use the Law of Cosines to solve the problem. A ship travels due west for 83 miles. It then travels in a northwest direction for 111 miles and ends up 165 miles from its original position. To the nearest tenth of a degree, how many degrees north of west did it turn when it ...
*March 18, 2016*

**maths**

If the faster pipe takes x hours, then we have to look at how much of the pool is filled each hour. 4/x + 9/(x+10) = 1/2 Now solve for x, and then get x+10.
*March 18, 2016*

**math**

7x6
*March 18, 2016*

**algebra**

just put the words into math: 5n+10d+25q = 255 d = n+6 q = 2n now just solve for the values.
*March 17, 2016*

**algebra**

c = a+6 6a+4c = 184 now just solve for the values.
*March 17, 2016*

**Math**

If the different categories have no overlap, then the angle would be that fraction of 360° representing the group of interest. In other words, 190/(190+135+220) * 360 ≈ 125.5°
*March 17, 2016*

**Math**

64m^2 * (1yd/0.9144m)^2 / 13yd * 36in/yd = 211.97 in
*March 17, 2016*

**Geometry**

(e+f)/(a-d) = b/a clear the denominators (also known as cross-multiplying) (e+f)a = b(a-d) or, (e+f)/b = (a-d)/a Looks like the first one is good.
*March 17, 2016*

**Math**

25 3/4 + x = 56 that should help...
*March 17, 2016*

**Math**

their combined speed is 252/4.5 = 56 mi/hr Now you can find the desired speed.
*March 17, 2016*

**math**

a+b+c = 408 b = c+7 b = a+5 now crank it out.
*March 17, 2016*

**math**

49-14 = 35 35/7 = 5 49+35 = 84 84+40 = 124, which is a good estimate
*March 17, 2016*

**Chemistry**

1 molecule of Zn(OH)2 has 3 ions, so the number of ions in 3 moles is 3*3*6.02*10^23
*March 17, 2016*

**Chemistry**

well, 0°C = 273.15°K
*March 17, 2016*

**math help pls pls**

when x=0, the worker has zero hours. So, the y-intercept is the cost of the insurance only. when x=0, 8x+25=25, so the choice is clearly (c)
*March 17, 2016*

**science **

You wish to obtain a magnification of -2 from a convex lens of focal length f. The only possible solution is to?
*March 17, 2016*

**math**

well, it's hard to say. 36/9+48-10/2 = 4+48-5 = 47 36/9+(48-10)/2 = 4 + 38/2 = 4+19 = 23 There are other possibilities, but those two seem the most likely to me.
*March 17, 2016*

**Math**

I don't see the diagram, so I can think of many possible answers, all the way from 45 to 125.
*March 17, 2016*

**music**

#1 surely not A. It is, after all, the KEY SIGNATURE! C is correct. C major is the same key as A minor. #2 cadence is the close of a phrase. C - the phrase is what stands on its own.
*March 17, 2016*

**Math**

correct.
*March 17, 2016*

**mathematics**

Draw radii bisecting both chords. Draw radii to the ends of the chords. Now you have right triangles with the hypotenuse equal to the radius. All the triangles are 5-12-13 So, do the math...
*March 17, 2016*

**Math**

again? See your earlier post. http://www.jiskha.com/display.cgi?id=1458203016
*March 17, 2016*

**Math**

put it all over a common denominator, and you have 2x(2x+3) + 1(x-3) + (3x+9) ---------------------------------- (x-3)(2x+3) as long as x is not 3 or -3/2, the fraction is zero when the numerator is zero. So, now you just have to solve...
*March 17, 2016*

**Math**

see your earlier post: http://www.jiskha.com/display.cgi?id=1458203016
*March 17, 2016*

**math**

Nope. -1 3/4 < -3/4 Better take a gander at C
*March 17, 2016*

**math**

Nope. A is exactly the reverse. Check again on comparing negative numbers.
*March 17, 2016*

**Advance Math**

wolframalpha shows many ways of writing the result: http://www.wolframalpha.com/input/?i=%28ln%283i%29%2F%282%2Bj%29%29^%281%2Fi%29 Using i instead of j, ln(3i) = ln3 + π/2 i = 1.917cis(0.96) 2+i = 2.236cis(0.46) ln(3i)/(2+i) = 0.857 cis(0.50) 1/i = -i, so that is 1/0.857...
*March 17, 2016*

**maths**

By "a 2" I assume you mean one or two 2's. both rolls: 1/6 * 1/6 = 1/36 1st roll only: 1/6 * 5/6 = 5/36 2nd roll only: 5/6 * 1/6 = 5/36 total: 11/36
*March 17, 2016*

**Math**

6: white without stereo dark interior
*March 17, 2016*