Wednesday

April 1, 2015

April 1, 2015

Total # Posts: 30,244

**stats**

you can play around with Z table stuff here: http://davidmlane.com/hyperstat/z_table.html
*January 26, 2015*

**Statistics**

try playing around here: http://davidmlane.com/hyperstat/z_table.html
*January 26, 2015*

**Calc**

This is also easy to see since cos(1/x) never exceeds 1. So, e^cos(1/x) never exceeds e. So, |e^cos(1/x)| <= e x e^cos(1/x) <= e*x -> 0 as x->0
*January 25, 2015*

**Math**

What you should do is read the problem carefully. It states that there are more than 50 marbles in the bag. So, what is the smallest multiple of 7 that is greater than 50? Must be 56.
*January 25, 2015*

**phisics**

mass * distance must be equal, so 18x = 36*0.45
*January 25, 2015*

**Calculus**

Since |(sin 1/x)| <= 1 |e^(sin 1/x)| <= e so x e^sin(1/x) <= x * e -> 0 as x->0
*January 25, 2015*

**Physics (Classical)**

using vectors, John's velocity is <0,-6.7> Mary's velocity is <-6.43,-9.53> Mary's velocity with respect to John is the difference between their velocities: <-6.43,-9.53> - <0,-6.7> = <-6.43,-2.83> Now just get the magnitude and ...
*January 25, 2015*

**Math**

840 * 2/3 = 560 840-560 = 280 half of 280 = 140 560+140 = 700
*January 25, 2015*

**Algebra I**

it lands when the height (y) is zero. So, just solve for x in -0.02x2 + 2.3x + 6 = 0 just use the quadratic formula.
*January 25, 2015*

**math**

(1 - 1/4 - 1/2(3/4))x = 800
*January 25, 2015*

**algebra**

you are correct if you meant [2(-2)-4(-3)]/(5-8)
*January 25, 2015*

**Physics**

First unify the units. 55.4 mi/hr = 24.8 m/s you know that the distance is given by s = 24.8t - 1/2 at^2 So, to stop in exactly 116 meters, we need 24.8t - 1/2 at^2 = 116 Now, we know that during that time, the speed reduces from 24.8 m/s to zero, so a = 24.8/t m/s^2 t = 24.8/...
*January 25, 2015*

**Math**

li spent $840 on vacation, She spent 2/3 of the amount on a train ticket and 1/2 of the remaining amount on food. How much did she spend on ticket and food altogether?
*January 25, 2015*

**Math**

sam travelled 1/4 of a journey by bus. he jogged 1/2 of the remaining distance and walked the rest of the way. If he walked 800 feet, what was the total distance he traveled?
*January 25, 2015*

**Algebra 2 Applications**

If you want to include the travel time of the sound, you have to look up the speed of sound in air. Let's say that is 343.2 m/s. So now, if the falling time is t, then we have 4.9t^2 = 343.2(3-t) t = 2.88 So, the balloon fell for only 2.88 seconds, making the distance 4.9*...
*January 25, 2015*

**physics**

well, you know that the height is y = 45t - 4.9t^2 Now just use that parabola to answer the questions.
*January 25, 2015*

**math**

If the four got amounts a,b,c,d respectively, then a = 2b b = 3c c = d/2 a+b+c+d = 840 a-d = 280
*January 25, 2015*

**math**

1day/L * 1000L/kL * 1year/365day = 1000/365 years.
*January 25, 2015*

**math**

since the denominator is not zero at t=2, just plug in t=2 to get the limit. The function is continuous at t=2. (2^44-9)/9
*January 25, 2015*

**Algebra**

I assume you mean 1/(1-2x) + 6x/(1+2x) = 3 the common denominator is (1-2x)(1+2x), so we get (x ≠ ±1/2) (1+2x) + 6x(1-2x) = (1-2x)(1+2x) 8x^2 - 8x = 0 8x(x-8) = 0 I expect you can take it from there, right?
*January 25, 2015*

**Calculus**

as you figured, the time t is t = (300-x)/(160) + √(800^2 + x^2)/70 dt/dx = 160x - 70√(800^2 + x^2) ----------------------------- 70*160√(800^2 + x^2) dt/dx=0 when 160x = 70√(800^2 + x^2) 25600x^2 = 56000000 + 4900x^2 x = 389.23 Hmm. Not what I had ...
*January 25, 2015*

**Maths**

x(t) = 0 if the object is at rest where it started. Don't you think you need to specify a bit more abut the situation?
*January 25, 2015*

**maths**

I think you have left something out. An = An-1 + 96
*January 25, 2015*

**math**

No, it would be y >= x+3 You have to include the number of female birds. There are at least three more males than that.
*January 25, 2015*

**math**

these are just simple polynomial addition, subtraction and multiplication. (f*g)(x) = f(x)*g(x) = (x+4)(3x+2) and the same for the other operators.
*January 25, 2015*

**Math**

tan π/4 = 1, so 4x = π/4 (1/√2,1/√2) period = π/4 x = π/16 + n(π/4) for the second, you just have cscx =0 or secx = 2 and proceed as above
*January 25, 2015*

**maths**

you know that the difference between terms is constant, so (4x+5)-(x) = (10x-5)-(4x+5) now just solve for x.
*January 25, 2015*

**math function2**

A) 18-6 = 12 seconds B) no idea of the radius. You give no indication of the height of the wheel, or where the platform is in relation to the axle. C) no can do. All we know is that h(t) = A + Bsin(pi/6 t + C)
*January 25, 2015*

**Algebra Ques23**

I can't imagine the math class where you have exercises in trigonometry, algebra, calculus, and such a simple question as this. Also, I get tired of your homework dumps with no effort on your part.
*January 25, 2015*

**Trig 4**

no. They are just ratios in a right triangle. Review your text, where I'm sure it is explained clearly. Google is your friend.
*January 25, 2015*

**physics**

clearly, the resultant is max if they act in exactly the same direction. So, what do you think?
*January 25, 2015*

**Mathematics (Vector) (ENGG1410)**

they are just ellipses parallel to the xy plane.
*January 25, 2015*

**College Trigonometry**

You can also read the excellent article on "trajectory" in wikipedia, where these equations are derived.
*January 25, 2015*

**Math**

you don't need to sum the series. It doubles 8 times in 24 hours, so the population is 40*2^8. You'd only need the sum if a new population, double the old one, was added every 3 hours. The runner problem is just the same. Every day you multiply the distance by 1.1 So, ...
*January 24, 2015*

**math**

just use the quadratic formula.
*January 24, 2015*

**maths**

Think of the hexagon as six equilateral triangles. The altitude of each triangle is 24. So, the side of each triangle (equal to the sides of the hexagon are) 48/√3
*January 24, 2015*

**Trigonometry**

No idea which angle sigma is, but I'll assume it's C, since otherwise you'd probably have used alpha. sinA/a = sinC/c so, sinA/28.1 = .4617/52.8 sinA = .2457 A = 14.2° or 165.3° Now you can find B and b.
*January 24, 2015*

**Algebra Rearrangement**

it's a quadratic in x: rx^2-tx-h = 0 use the quadratic formula to find the value(s) of x.
*January 24, 2015*

**math**

(c ¢)/(1 lb) * (a oz) * (1 lb)/(16 oz) = ac/16 ¢
*January 24, 2015*

**math**

1/(9+3+1)
*January 24, 2015*

**Geometry**

Pick up a real cube and draw a 3x3 grid one each face. Fill in the grids on 3 faces with R and 3 with B. The very center cubelet has no painted faces. Now count the others and total up the various color combinations. Make sure that it makes no difference how the two colors are...
*January 24, 2015*

**Pre Calculus**

Review the idea of reference angles, which are always in QI. sin 0.0135 = 0.0135 That is the angle in QI. But sin is negative in QIII and QIV. So we have π+0.0135 and 2π-0.0135 cot 0.351 = 2.731 But, cot is negative in QII and QIV, so we have π-0.351 and 2π...
*January 24, 2015*

**Math**

It appears that the chopped piece fell 4 feet. So, the tree was 4+7=11 feet tall.
*January 24, 2015*

**physics**

the height of the falling stone is 6.82-8.8t-4.9t^2 the height of the stone thrown upward is 8.8t - 4.9t^2 So, when do they meet? At t=0.3875 Now plug that into either function to get the height at that time. http://www.wolframalpha.com/input/?i=solve+6.82-8.8t-4.9t^2++%3D++8....
*January 24, 2015*

**physical**

√((300+400/√2)^2+(400/√2)^2)
*January 24, 2015*

**maths**

34.67*10^-6 pN/m^2 * 1.0197*10^17 lb/pN * 2.59*10^6m^2/mi^2 = 9.16*10^18 lb/mi^2
*January 24, 2015*

**Set Question 1**

Since A∩(BC) = A∩B ∪ A∩C, your first step is (X ∪ Y ∪ Z)∩X ∪ (X ∪ Y ∪ Z)∩(Y∩Z) and now break down each of those similarly. Just review your basic set properties. Recall that X∪X = X∩X = X
*January 24, 2015*

**Trignometery**

As usual, draw a diagram. If we label Kappy=K Blue UFO=B Red UFO=R KR = 42 tan64° + 42 tan 12° UV = 42(sec 12°)
*January 24, 2015*

**Algebra**

39,916,799 http://www.wolframalpha.com/input/?i=sum+n*n!+for+n%3D1+to+10
*January 24, 2015*

**Geometry**

the tangent at P has slope x/(2a) So, the normal line is y-ap^2 = p/(2a) (x-2ap) y = p/(2a)(x-2ap)+ap^2 So, where does that line intersect y = x^2/(4a) ? p/(2a)(x-2ap)+ap^2 = x^2/4a (1/4a)x^2 - p/(2a)x + p^2(1-a) = 0 Now just solve that for x and figure y. One solution better ...
*January 24, 2015*

**math**

no idea. where did you leave off? Just start with 8 and keep adding 3
*January 24, 2015*

**Math**

1A reflection in the x-axis changes the sign of y. parent: x^3 flip over x: -x^3 raise 2: -x^3+2 2C y becomes taller, which has the equivalent effect of making the graph look narrower. parent: x^2 shift right (x-2)^2 flip over x: -(x-2)^2 stretch up (make narrower): 3(x-2)^2 ...
*January 24, 2015*

**math**

If the rectangle's dimensions are x and y, and the square is side s, then 2x+2y = 4s 2(x+y) = 96 x = s-4 2(x+y) = 2x+2y = 4s = 96 so, s = 24 x = s-4 = 20, so y = 28 2xy = 2*20*28 = 1120
*January 24, 2015*

**math**

If the cardboard has side x, the volume is (x-8)^2*4 = 324 Now it is clear what x is.
*January 24, 2015*

**algebra**

(x - 1/5)^2
*January 23, 2015*

**Maths**

a = 4 d = 11 n = (368-4)/7 + 1 = 53 S53 = 53/2 (4+368) = ?
*January 23, 2015*

**algebra**

Using feet for all measurements, we have 18 * 3/4 * length = 4*27*4 length = 32 ft
*January 23, 2015*

**algebra**

2.50(5/4) + 5.50(3/4) = x(5/4 + 3/4) x = $3.625
*January 23, 2015*

**applied math**

width is 10*12 = 120 inches So, it takes 120/4 widths Since the wall is an exact number of widths, we just need to figure the length to find the rolls. 10*12*4 = 480 in long so, we need 480/(20*12) = 2 rolls Makes sense, since each roll does 2 strips, and we need 4 strips.
*January 23, 2015*

**algebra**

I get 0.808
*January 23, 2015*

**Math**

P = (8,-3) The slope of PQ is ∆y/∆x = (3/(7-x)-(-3))/(x-8) = (3+3(7-x))/((7-x)(x-8)) = (24-3x)/((7-x)(x-8)) You have provided no data about Q or the desired slope, but just plug in the numbers you have.
*January 23, 2015*

**math**

using the two-point form of a line, you have (p-59) = (42-59)/(50-32) * (q-32) Now just rearrange that into p = 1/18 (1606-17q)
*January 23, 2015*

**Algebra 1**

You know two things: g+s = 425 g = s+25
*January 23, 2015*

**college algebra**

just solve for t in 16t^2 = 128
*January 23, 2015*

**Math**

you have a right triangle with legs 4 and 6. The hypotenuse is thus 2√13. I don't see any good choices.
*January 23, 2015*

**math**

you have the line intersecting when kx^2-5x+2 = -3x+4 kx^2-2x-2 = 0 Now recall the discriminant, d=b^2-4ac If d>0 there are two roots If d=0, there is one root If d<0 there are no real roots. The discriminant of your equation is 4+8k I expect you can determine when that ...
*January 23, 2015*

**Math**

if it takes t seconds to flip it once, then the actual flipping will take 10,000*t or 100,000*t seconds. There are 86,400 seconds in a day, if that helps.
*January 23, 2015*

**math**

a = 12 d = -6 T30 = a+29d so, . . .
*January 23, 2015*

**math**

I love it when you guys as us to show our work. Ever think of showing some of yours? y' = 6x+4 The line given has slope -2. So, when do we have 6x+4 = -2? x = -1 y(-1) = -2, so we want the point (1,-2) to be on the line. That means -2 = -2(-1)+b b = -4 See the graphs at ...
*January 23, 2015*

**College Algebra**

6400(1+.005/12)^(12*7) = $6627.92
*January 23, 2015*

**Math**

I'll do one, and you follow the steps for the other. 2cosx + √2 = 0 cosx = -√2/2 = -1/√2 x = π/4 on the unit circle, x = cosθ and y = sinθ, so the location is (-1/√2,1/√2) or (-1/√2,-1/√2) (QII or QIII) as usual, ...
*January 23, 2015*

**integrated physics and chemistry**

(12-20 m/s)/(32s) = -8/32 = -0.25 m/s^2 However, as the car was going north and slowed down, its acceleration was in the south direction.
*January 23, 2015*

**maths**

s = rθ you have r and θ, so plug them in (θ in radians). That will give you the actual arc length traveled. If you want the horizontal distance, assuming symmetry, then you will need x/2 = r sin(θ/2)
*January 23, 2015*

**math**

just equate the two: 2x^2-2x-3 = -x^2-2x-3 2x^2 = -x^2 x = 0 so, y = -3
*January 23, 2015*

**math**

clearly it is a geometric series, with a = 2 r = 3/7 So, use your summation formula for GP's: Sn = a(1-r^n)/(1-r) and plug in a and r.
*January 23, 2015*

**Maths - eh?**

No idea what xsq is. x^2? And what is the triple "xsq, ysq, z,sq" supposed to mean? I'll use © for the operator. You say (x,y,z)© = xsq, ysq, z,sq I have no idea what that means. Is it x^2+y^2+z^2? Gotta help me out here.
*January 23, 2015*

**Cgs**

x(t) = 9t - 1/3 t^3 + c since x(1)=2, 2 = 9 - 1/3 + c c = -20/3 x(t) = 9t - 1/3 t^3 - 20/3 when v=0, the particle has changed direction. That is when t=3. So, now just evaluate x(3).
*January 23, 2015*

**Math**

if you add the two equations, you get 5x = 20 I think you can solve that, eh?
*January 23, 2015*

**Relative Extrema: AP Calculus**

f = (3/4)x^4-x^3-3x^2+6x f' = 3x^3-3x^2-6x+6 f" = 9x^2-6x-6 extrema where f'=0 and f"≠0 f increasing where f' > 0 there are two inflection points because f" has two real roots.
*January 22, 2015*

**Antiderivatives**

Close, but no cigar. For powers, raise it by one and divide by it. So, F(x) = 1/6 x^6 -4(1/-2) x^-2 - 4x + c = 1/6 x^6 + 2x^-2 - 4x + c Since F(1) = 1, 1 = 1/6 + 2 - 4 + c c = 17/6 F(x) = 1/6 x^6 + 2x^-2 - 4x + 17/6 Frankly, I think the negative exponent is a typo, but that&#...
*January 22, 2015*

**Math**

You find out your faucet is leaking 10 pints of water every 3 hours. After 6 hours, how many gallons of water will have leaked from the faucet? How do I solve this problem?
*January 22, 2015*

**Math**

5-2*(6-(4+2))=5 Still thinkin' on the other one
*January 22, 2015*

**help math algebra**

for addition and subtraction, just collect terms with the same power (7a^5-a^3)-(a^5-5a^3-1) 7a^5-a^3-a^5+5a^3+1) (7-1)a^5 + (-1+5)a^3 + 1 4a^5 + 4a^3 + 1 When multiplying, use the distributive property (5x-3)(x^3-5x+2) (5x)(x^3-5x+2) - 3(x^3-5x+2) 5x^4-25x^2+10x-3x^3+15x-6 5x...
*January 22, 2015*

**Math**

1.50n + 2.00+1.25n
*January 22, 2015*

**Math**

standard form does not involve an intercept. The standard form for a line is Ax + By = C You have done it correctly. And, the intercept was given. It is zero.
*January 22, 2015*

**geometry**

has 5 sides of length 9 ft each
*January 22, 2015*

**geometry**

KL/JL = tan 24° you know KL, so now just solve for JL.
*January 22, 2015*

**Algebra 1**

Thank you
*January 22, 2015*

**Algebra 1**

Does the table represent an expoential function? x 1 2 3 4 y -1 -8 -27 -64 yes or no my answer is no
*January 22, 2015*

**math**

T5/T2 = r^3, so r^3 = (x^4/8)/(4x) = x^3/32 r = x/∛32 I suspect a typo, but we'll go with what we have. T10 = T5 r^5 = x^4/8 * x^5/(256∛2) = x^9/(2048∛2)
*January 22, 2015*

**Math**

It's good. You don't really need the leading "-" if you say a is negative, but having it there does signal your intentions clearly.
*January 22, 2015*

**College Algebra**

read the "trajectory" article at wikipedia.
*January 22, 2015*

**Math**

#1 is always true. Draw a triangle. Extend one side so that you can see the interior and exterior angles. They add up to a straight line (the extended side). Thus they are supplementary. #2 sometimes #3 never Have you tried drawing the triangles to illustrate the ideas?
*January 22, 2015*

**hw dump**

I've done a couple. How abut you show some work of your own, rather than just doing a homework dump?
*January 22, 2015*

**math**

2x+(3x-(4x-5))=x/4-2 2x+(3x-4x+5)=x/4-2 2x+(-x+5) = x/4 - 2 x+5 = x/4 - 2 3x/4 = -7 x = -28/3
*January 22, 2015*

**math - bogus**

x^2 + y^2 = 20 xy = 192(39.37^2) = 297600 Clearly x and y are less than 20. No way could their product be so huge. I suspect a typo.
*January 22, 2015*

**math**

The nth row has 35-4(n-1) = 39-4n plants. So, what is the largest multiple of 4 less than 39? Subtract that from 39. Or, just divide 39 by 4. The remainder is how many plants are in the last row. It is the row that is too short to subtract 4 from it again.
*January 22, 2015*

**calculus**

v(t) = ds/dt = 50-4t find t when v=0
*January 22, 2015*

**math**

.99(1.05)
*January 22, 2015*

**Geometry**

If the longer ladder is x, and reaches up y feet on the wall, then 8.3^2 + y^2 = x^2 8.3^2 + (y-9.1)^2 = (x-7.2)^2 x = 17.9
*January 22, 2015*

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