Monday

July 27, 2015

July 27, 2015

Total # Posts: 32,481

**math**

total water: (4*.750 + 2*1.5)L at 1L/min, how long is that?
*May 5, 2015*

**science**

(5000+750)/(180) servings I'll let you decide how much is left over
*May 5, 2015*

**Calc**

h(t) = 200 + 40t - 16t^2 now work your magic on (b) and (c)
*May 5, 2015*

**Math**

both wrong. see earlier post.
*May 5, 2015*

**Math**

if the roots are a and b, the function is (x-a)(x-b) = 0 So, plug in a=(2+√5)/3 b=(2-√5)/3
*May 5, 2015*

**336**

Bzzzt, but thanks for playing! since the number of messages is an integer, it is clearly discrete since time can take on any value, it is continuous
*May 5, 2015*

**math**

repeated multiplication x^2 = x * x x^3 = x * x * x and so on
*May 5, 2015*

**Math**

reflection in the y-axis takes (x,y) -> (-x,y) Just fold the paper along the y-axis and see what the points do.
*May 5, 2015*

**Math**

you have y = (x-a)^2 - b so, (x-a)^2 = b x = a±√b = (k/2)±√((k-2)^2/4) = (k/2)±(k-2)/2 = k/2 + k/2 - 1 = k-1 or k/2 - k/2 + 1 = 1 check x=1: (1-(k/2))^2 - (k-2)^2/4 (2-k)^2/4 - (k-2)^2/4 0
*May 5, 2015*

**math**

guess you missed the deadline, eh? 5 kinds, choose 3. Sound familiar?
*May 5, 2015*

**Probability**

clearly, based on the 69 draws, P(pink) = 36/69 P(brown) = 33/69
*May 5, 2015*

**Math**

That's the same as the number of ways to select 6 items all at once, then read them once a week. 20P6 Unless you are allowed to choose the same book more than once. Then the number is 20^6
*May 5, 2015*

**Math**

There are 20 books on a summer reading list. In how many ways can you choose 1 per week for 6 weeks.
*May 5, 2015*

**Math**

well, how many perfect squares or odds are there in 1..8?
*May 5, 2015*

**Math**

You spin a spinner that has 8 equal sections numbered 1 to 8.Find p(perfect square or odd).
*May 5, 2015*

**math**

given your matrix A, we need to solve det(nI-A) = 0 so we need to solve |n-1 -1 0 0| |-1 n-1 0 0| |0 0 n 0| |0 0 0 n| = 0 That is n^3(n-2) = 0 As you can see, n = 0,0,0,2
*May 5, 2015*

**Math**

6 6/7 is near 7 4 2/7 is near 4 1 3/5 is near 1 3/4 = 7/4 4 * 7/4 = 7 Sounds good to me as an estimate
*May 5, 2015*

**trigonometry**

I AM WRONG >
*May 5, 2015*

**trigonometry**

How about some parentheses, so we can tell what's what? As it stands, it means 1 + tan2A = cosA + tanA - sinA which is clearly false
*May 5, 2015*

**functions**

you want R where k/R^2 = 10(k/r^2) R^2/r^2 = 1/10 R/r = 1/√10
*May 5, 2015*

**functions**

v = x(10-2x)(20-2x)
*May 5, 2015*

**Math**

so, now you can figure how many miles the light travels in 7200 seconds, right?
*May 4, 2015*

**Math**

well, how many seconds in 2 hours?
*May 4, 2015*

**Math**

42
*May 4, 2015*

**math**

you need 2/x < x/22 44 < x^2 so, 6 < x Now, you need x/22 < 0.33 x < 7.32 So, we have x = 7 2/7 < 7/22 < .33 Do the other in like wise.
*May 4, 2015*

**Algebra**

what's the problem? Just start working out the values: a1 = -2 a2 = 2(a1)^2 = 2(-2)^2 = 8 a3 = 2(a2)^2 = 2(8)^2 = 128 ... a1 = ln(e^2) = 2 a2 = ln(e^4) = 4 ... b0 = 1 b1 = 2 b2 = 2(2)-1 = 3 b3 = 2(3)-1 = 5 ...
*May 4, 2015*

**math**

it will be a line sloping upward, passing through (0,-4)
*May 4, 2015*

**Math**

the intersection(s) will be where x^2 + (x+k)^2 - 25 has one solution. That is, where the discriminant is zero. x^2 + x^2 + 2kx + k^2-25 = 0 2x^2 + 2kx + (k^2-25) = 0 The discriminant is (2k)^2 - 4(2)(k^2-25) 4k^2 - 8k^2 + 200 = 0 k^2 = 50 k = ±√50 So, check out ...
*May 4, 2015*

**Math**

y = 4(x^2+6x)-5 = 4(x^2+6x+9) - 5 - 4*9 = 4(x+3)^2 - 41 The vertex is at (-3,-41), and the parabola opens upward, y cannot be less than -41. Did you actually try plugging in, say, 7=700 to see whether there was a solution there?
*May 4, 2015*

**Math**

correct
*May 4, 2015*

**Algebra**

do this just like the ellipse in your earlier post. That is, complete the squares, then review your text about hyperbolas. 36x^2-24x - (y^2-6y) = 41 36(x - 1/3)^2 - (y-3)^2 = 41 + 36/9 - 9 (x-1/3)^2 - (y-3)^2/36 = 1
*May 4, 2015*

**Math**

Switching dircetion is just a shorthand way of moving stuff from one side to the other: -4k > -36 add 4k to both sides: 0 > 4k-36 add 36 to both sides: 36 > 4k or, as you saw above, 4k < 36 k < 9 multiplying and dividing by a negative value change the direction...
*May 4, 2015*

**Algebra**

for this ellipse, the major axis is vertical. a = 3 b = 2 The vertices are at (-3,1±3) The co-vertices are at (-3±2,1) Looks like it's time to review your ellipses.
*May 4, 2015*

**Algebra**

rearrange stuff and complete the squares: 9x^2+54x + 4y^2-8y = -49 9(x^2+6x) + 4(y^2-2y) = -49 9(x^2+6x+9) + 4(y^2-2y+1) = -49 + 9*9 + 4*1 9(x+3)^2 + 4(y-1)^2 = 36 (x+3)^2/4 + (y-1)^2/9 = 1 Now answer the questions.
*May 4, 2015*

**geometry - eh?**

what is the "lip"? and where is your punctuation?
*May 4, 2015*

**Math**

F = ma
*May 4, 2015*

**Math**

so, if you have the answer, why are you posting the question? Check out the Pythagorean Theorem. x^2+y^2 = 1600 x+y+40 = 96.22
*May 4, 2015*

**Math**

2r+h = 25 a = πr(r+2h) = πr(r+25-2r) = π(25r-3r^2) da/dr = 0 when r = 25/3 d = 2r = 50/3 h = 25 - 50/3 = 25/3
*May 4, 2015*

**Math**

x+y = 37 x^2+y^2 = 765.5 x^2+(37-x)^2 = 765.5 2x^2 - 74x + 603.5 x^2 - 37x + 301.75 = 0 x = (37±9√2)/2 x = 12.1, 24.8 Hmmm. I don't get their answers either, but I'm a lot closer than you. What did you do?
*May 4, 2015*

**geometry**

the diameters are in the ratio 5:6 the larger is 12, so the smaller is 10 the smaller cone has height h=3, so the larger cone has height 3*(6/5) = 18/5
*May 4, 2015*

**Math**

Laid out on the x-y plane, the track's line can be described by y = 400 - 2/3 x So, if the rectangle has one corner on the line and the opposite corner at (0,0), its area is a = xy = x(400 - 2/3 x) = 400x - 800/3 x^2 This is just a parabola. Find its vertex, and that is ...
*May 4, 2015*

**Calculus**

all of them? f is concave down with a max at x = -3
*May 4, 2015*

**math**

divide the total amount by the amount needed for each batch, giving the number of batches: 6/(2/3) = 6 * 3/2 = 9
*May 4, 2015*

**geometry**

Recall your rotation matrix. (x,y) -> (x',y') where x' = xcosθ - ysinθ y' = xsinθ + ycosθ So, plug in your θ. You can easily check your work by noting that the point will rotate down to the x-axis.
*May 4, 2015*

**math**

300*1.04^5
*May 4, 2015*

**alg**

no ideas? Review your conic sections and show us whatcha got.
*May 4, 2015*

**math**

since the dice are independent events P(odd,odd) = 1/2 * 1/2
*May 4, 2015*

**math**

$5200 / $6.50/m = 800m of fence maximum area for a given perimeter is a square, so we have an isosceles right triangle with both legs 400m long.
*May 4, 2015*

**math**

#1 clearly the circle is of radius 5. So, since x^2+y^2 = 5^2, (0,5) lies on the circle. the center is the midpoint of AC: (0,0) so, the radius is 13. 0^2+13^2 = 13^2 7^2 + (2√30)^2 = 49+120 = 13^2 so, all vertices lie on the circle.
*May 4, 2015*

**critical points**

critical values are where f' = 0 or undefined. f'(x) = 18x^2-18 = 18(x^2-1) So, where is f' = 0?
*May 4, 2015*

**math**

a = s^2 da = 2s ds
*May 4, 2015*

**trigonometry**

You can expand both binomials, and watch things cancel out, or note that 2sin^2(45+A) = 1-cos(90+2A) 2sin^2(45-A) = 1-cos(90-2A) cos(90+x) = -sinx cos(90-x) = sinx Now just add it up.
*May 4, 2015*

**math**

v = (12-2x)(16-2x)x dv/dx = 4(3x^2-28x+48) set dv/dx=0 and solve for x.
*May 4, 2015*

**math**

it reverses direction when v changes from + to - v(t) = 3t^2-18t+24 = 3(t^2-6t+8) = 3(t-2)(t-4) So, where does v(t) cross the axis and become negative? Now use that value to find s(t) and a(t)
*May 4, 2015*

**Physics**

1/48 + 1/di = 1/110 M = 110/(110-48)
*May 3, 2015*

**calc (please help)**

I'm assuming that the angle between the planes is situated on the edge of the cylinder, so that the two planes intersect the cylinder in a circle and an ellipse. So, the ellipse has major axis of length 2r secβ, and the far side of the major axis is a distance 2r tan...
*May 3, 2015*

**Math--ONE QUESTION**

well, -14 = -9-5 0 = 8-8 So, what do you think?
*May 3, 2015*

**Calculus max/min**

If you walk directly to a point x feet from the bus stop, your walking distance is park: √(600^2+(2000-x)^2) sidewalk: x so, your time taken (distance/speed) is t(x,d) = √(600^2+(2000-x)^2)/(3.5+d) + x/(5.5+d) t(x) = √(600^2+(2000-x)^2)/4.267 + x/7.267 so, ...
*May 3, 2015*

**Math Trigonometric Identities**

if you set the left side over a common denominator of sinx, you have 1/sinx - sin^2x/sinx (1-sin^2 x)/sinx If that does not get you started, I don't know what will...
*May 3, 2015*

**Math Trigonometric Identities**

that is correct, but it would have been simpler when you got the LS expanded, to see that you had LS = sin^2x - 2sinxcosx + cos^2x = sin^2x + cos^2x -2sinxcosx = 1 - 2sinxcosx
*May 3, 2015*

**Earth Science**

the magnification of a telescope is changed by changing what? my answer is the eyepiece
*May 3, 2015*

**Math**

well, just plug in 180 = pi
*May 3, 2015*

**Math**

Since you are actually performing the action, I'd have to go with Experimental. If asked just to calculate the probability, then it would be theoretical. The actual observations might or might not agree with the calculation. In fact, for any finite number of trials, the ...
*May 3, 2015*

**Math**

why all those words? Try using a little actual notation: If tan A = a / b, a>0, b>0, and 0<A<pi/2, then what is cos A? a. a / b B. b / a C. a / √(a^2 + b^2) D. b / √(a^2 + b^2) E. √(a^2 + b^2) / b given tanA = a/b, you know that opposite side is a...
*May 3, 2015*

**Algebra**

add up the coins, and add up the values: n+d = 29 5n+10d = 230 Now just solve for n and d.
*May 3, 2015*

**Algebra**

done. see related questions below
*May 3, 2015*

**Calculus 2**

This looks suspiciously like 1/5 e^x which converges everywhere.
*May 3, 2015*

**Calculus - more data**

Is the intersection of the planes tangent to the curved edge of the cylinder? Which axis is the axis of the cylinder? the y-axis? If so, why mention it by name?
*May 3, 2015*

**Calc 1**

the base has area 2w^2 The volume is 10, so the height h=5/w^2 So, the cost is 13(2w^2) + 10(wh + 2wh) = 26w^2 + 10w(3h) = 26w^2 + 10w(5/w^2) = 26w^2 + 50/w
*May 3, 2015*

**Math**

cost: 4.50*14 revenue after spoilage: 10p we want 10p = 4/3 (4.50*14) p = 8.40
*May 3, 2015*

**Calc 1**

oh, please. Surely you can describe the diagram. As a calculus student, you have surely developed some skill with language as well.
*May 3, 2015*

**Calc 1**

no diagram. How about a description? I can guarantee that the maximum area is achieved when the fencing is divided equally among lengths and widths.
*May 3, 2015*

**Math**

Equal divisions: x receives $500 Proportional: x receives 4500/(4500+4500+1000) * 1500 = $675
*May 3, 2015*

**Math**

Just look at the ratios: 1/2 = 0.5 .5/1 = 0.5 .25/.5 = 0.5 ... So, the next number is .125 * .5 = .0625 It might have been easier using fractions. The sequence is thus seen to be 2, 1, 1/2, 1/4, 1/8, ...
*May 3, 2015*

**math**

I think the related questions below will provide the method of solution.
*May 3, 2015*

**Math**

a/b = 3/4 c/b = 1/2, so b/c = 2/1 and thus a/c = a/b * b/c = 3/4 * 2/1 = 3/2
*May 3, 2015*

**Math. first and last repost. please help**

done. see earlier post.
*May 3, 2015*

**maths**

8C5 = 8*7*6*5*4 ------------- 1*2*3*4*5 Note that this es equal to 8C3 = (8*7*6)/(1*2*3) because the 4*5 just cancels out. to figure nCm, just start with n, and count down for m factors in the top, and starting with 1, count up for m factors in the bottom. If m > n/2, you ...
*May 3, 2015*

**Math please help.**

Only the graph of a function has a slope. This and similar questions are extremely poorly worded. y has a greater rate of change. There is only one slope: that of the function. Its slope is 3. Only the function has a slope. x and y do not have slopes. They just have rates of ...
*May 3, 2015*

**math**

I only see one function: f(x) is (-1,0),(0,1),(1,2),(2,3) x and y change at the same rate. When x increases by 1, so does y.
*May 3, 2015*

**trigonometry**

120651/47 π = 2567.04 π So, tan(-120651/47 π) = -tan(120651/47 π) = -tan(2567π + 2/47π) = -tan(2/47 π) arctan(-tan(2/47 π)) = -2/47 π You are correct. x = a/√(25-a^2) son tan(arcsin(a/5)) = a/√(25-a^2) Always use the ...
*May 3, 2015*

**mth121**

2x+3y = 3 x-2y = 5 has solution (3,-1) This point is also on on the third line, so it is the solution to all three equations.
*May 3, 2015*

**Math 222**

a good place to start would be here. Does your text not have any examples of graphing functions? http://www.wolframalpha.com/input/?i=plot+y%3D-x%5E2%2C+y%3D%E2%88%9A%28x-1%29
*May 3, 2015*

**math**

y = -(10-x)^2+75 This is just a parabola with vertex at (10,75) So, the max height is 75 meters
*May 3, 2015*

**Maths**

The 4 points define a tetrahedron. What do you mean by "boxes" as related to the tetrahedron?
*May 3, 2015*

**trigonometry**

done. see earlier post.
*May 3, 2015*

**trigonometry**

just pull out your calculator. cos(1.50) = 0.07 Since cos x > 0 in QI and QIV, the other solution is 2π-1.50
*May 3, 2015*

**trig**

Trying to get past the copy/paste of strange fonts, I interpret the question as finding the trig functions of the angle whose terminal side is (√15,8) You have x=√15 and y=8, so r = √(15+64) = √79 Now just use the definitions sinθ = y/r cosθ...
*May 3, 2015*

**Math**

You don't need it. arctan(-x) = -arctan(x) So, now you want arctan(-tan(7/15π)) = -arctan(tan(7/15π)) = -7/15π
*May 3, 2015*

**Math**

tan(-22/15π) -tan(22/15π) -tan(π+7/15π) -tan(7/15π) not a recognizable value. As long as you have to use your calculator anyway, why nut just plug in the original value? You get -9.514 Or is there more to the question than what you posted?
*May 3, 2015*

**math**

Try this, which is a better rendering of the given statements: x+23 = 2y y+23 = 3z z+23 = 4x
*May 3, 2015*

**Physics Help Please**

just review your formulas. In particular, hi/ho = f/f-do 32mm/17m = 40mm/(40-do)mm 32/17000 = 40/(40-do) do = 21210mm = 21.21m
*May 3, 2015*

**Math**

let u = arcsin(x) then du = 1/sqrt(1-x^2) dx now your integrand is just 1/u du Think you can handle that one?
*May 3, 2015*

**physics**

since there is no friction, there is no horizontal force. Thus, no acceleration. So, think of Newton's 1st law of motion.
*May 3, 2015*

**Chemistry**

Given the very nature of the question, you must have studied some examples. Care to share your ideas on the topic?
*May 3, 2015*

**Trigonometry - PS**

However, since inverse trig functions have principal values (because they are multi-valued), you have to be careful. arctan(tan(3π/4)) = arctan(1) = π/4, not 3π/4. So, you need to reduce your fraction to see how many multiples of π you can discard, and then...
*May 3, 2015*

**PHYSICS**

That would be zero, of course. Care to rephrase the question?
*May 2, 2015*

**algebra 1**

with the exception of calling the vertex the axis of symmetry, yes. The axis always passes through the vertex, but it is not the vertex; the vertex is just a point. The axis has no minimum point; it is a line.
*May 2, 2015*

**algebra 1**

axis is the line x=0
*May 2, 2015*

**algebra--1 question**

recall that (a+b)^2 = a^2 + 2ab + b^2. So, (2√5+3√7)^2 = (2√5)^2 + 2(2√5)(3√7) + (3√7)^2 = 4*5 + 12√35 + 9*7 = 83 + 12√35
*May 2, 2015*