Sunday

December 21, 2014

December 21, 2014

Total # Posts: 27,663

**Math please help**

Just so you can check your work, you should come up with 1/8
*November 10, 2014*

**math**

5.6930 x 10^4
*November 10, 2014*

**pre calc**

f(x) = 6x^7 + 7x^6 f'(x) = 42x^6 + 42x^5 = 42x^5(x+1) so, now it's easy to see where f'(x) = 0
*November 10, 2014*

**Math Pre Calc Help**

(cos^4x -sin ^4 x)/(sin^2x) (cos^2x-sin^2x)(cos^2x+sin^2x)/sin^2x (cos^2x-sin^2x)(1)/sin^2x cos^2x/sin^2x - sin^2x/sin^2x cot^2x - 1
*November 10, 2014*

**College Math**

v0 t - 16t^2 = 0 when t=8, so 8 v0 - 1024 = 0 v0 = 128 Now just find the vertex of the parabola, at t = -b/2a which in this case is at t = v0/32 = 4 that sounds correct, since it is at half the time to hit. 4 sec up, 4 sec down. So, just find s(4)
*November 10, 2014*

**Pre-Calc/Trig**

y-intercept is where x=0: f(0) = 0 x-intercept is where y=0 y = x(4-x^2) = x(2-x)(2+x) So, the x-intercepts are at -2,0,+2
*November 10, 2014*

**Math 201 ( Algebra)**

If there are x at $40 and y at $80, then 40x+80y = 1000 x = y+80 Now just solve for x and y
*November 10, 2014*

**calculus**

if the square has side s and the circle has radius r, then r+s = 360 pi r^2 = (360-r)^2 (pi-1)r^2 + 720r - 129600 = 0 r = 129.85 ...
*November 10, 2014*

**Calculus**

y = x^(2/3) * ((5/2)-(x) y' = (2/3)x^(-1/3)*(5/2 - x) + x^(2/3)(-1) = 5(1-x) / (3*x^(1/3)) So, y'=0 when x=1 y" = -5(2x+1) / (9x^(4/3)) y"(1) < 0, so f(1) is a maximum See the graph at http://www.wolframalpha.com/input/?i=+%28x^2%29^%281%2F3%29+*+%28%285%...
*November 10, 2014*

**Calculus angle of elevation with elevator**

The two solutions below have exactly the same problem, and each step is shown. Where do you get stuck?
*November 10, 2014*

**Calculus angle of elevation with elevator**

see the related questions below - just change the numbers
*November 10, 2014*

**limerick poem**

oops - bad closing tag...
*November 10, 2014*

**limerick poem**

Just because it has five lines and rhymes, that does not make it a limerick. There is a certain very strict meter which must be followed. Read a bunch of them, then try again. Your meter is way off. The rhythm must be as in There was an old man from Nantucket Who kept all his ...
*November 10, 2014*

**Math! Algebra 1!**

If the still-water speed is s, then since distance = speed*time, then in equal time (say, t=1), (s+1.5) = 2(s-1.5) s+1.5 = 2s-3 s = 4.5 100/4.5 = 22.22 hrs or 22 hr 13 min 20 sec
*November 10, 2014*

**Calculus angle of elevation**

of course there is... when the elevator is x meters up, tanθ = (x-31)/22 So, sec^2θ dθ/dt = 1/22 dx/dt when x=20, tanθ = -11/22, so sec^2θ = 5/4 5/4 dθ/dt = 1/22 (3) dθ/dt = 55/6 m/s Is one of the steps unclear?
*November 10, 2014*

**Calculus angle of elevation**

see the related questions below. The first is the identical problem -- just change the numbers.
*November 10, 2014*

**math**

so, OHE = 3HER Sure you didn't leave something out?
*November 10, 2014*

**mathematics**

2OR = 2x+5 2OR = HE+5 HE = 2OR-5
*November 10, 2014*

**mathematics - incomplete**

can you not tell there is some missing information here?
*November 10, 2014*

**Science**

(8m/s)/(3s) = 8/3 m/s^2 (40m/s)/(8s) = 5 m/s^2 which is greater?
*November 10, 2014*

**Algebra**

the factors of -7 are -1 and 7 1 and -7 can you pick them so they add up to -6? (x+1)(x-7)
*November 10, 2014*

**math**

So, you must want the pair (cosθ,sinθ) which is the point on the unit circle associated with θ. 30: (0.866,0.5) 60: (0.5,0.866)
*November 10, 2014*

**math**

ok - I thought that might be it. So, now, what ordered pair did you have in mind? 30 degrees is just an angle. Is there supposed to be an ordered pair associated with an angle?
*November 10, 2014*

**math**

eh? Not sure what it is you are asking. ff?
*November 10, 2014*

**geometry - incomplete**

so, what is the question, again? You seem to have dropped some data, as well as what it is you are asking.
*November 10, 2014*

**math**

just write the data as given: a+b+c+d = 9000 a+c+d = 4b b+d = 4/5 (a+c) The first says that a+c+d = 9000-b using the second, that means that 9000-b = 4b b = 1800 So, now we have a+c+d = 7200 1800+d = 4/5 (a+c) Now we know that a+d = 7200-d, so 1800+d = 4/5 (7200-d) 1800+d = ...
*November 10, 2014*

**math(fractions)**

no idea. How long is the Blue Trail?
*November 10, 2014*

**calculus**

online, we generally use ^ for powers, and * for multiplication. Why bother changing the way it was posted? And the quotient rule says 5(3x+4)^4(3)(4x+1)^2 - (3x+4)^5(2(4x+1)(4)) ----------------------------------------- (4x+1)^4 (3x+4)^4 (15(4x+1)-8(3x+4...
*November 10, 2014*

**what is the rate of change of the angle of eleva**

see related questions below
*November 10, 2014*

**calculus**

when the elevator is x meters up, tanθ = (x-20)/20 So, sec^2θ dθ/dt = 1/10 dx/dt when x=10, tanθ = -1/2, so sec^2θ = 5/4 5/4 dθ/dt = 1/10 (5) dθ/dt = 2/5 m/s
*November 9, 2014*

**physics**

Look out below!! Was there a question in there somewhere?
*November 9, 2014*

**phyics**

If the tug pulls at speed v on a course of θ, then in x-y coordinates, 15 + 9cos60° + 35 sinθ = 0 19.5 + 35 sinθ = 0 sinθ = -0.5571 θ = N 33.9° W Now you can figure part B.
*November 9, 2014*

**Calculus**

revenue = price * quantity, so r = x(160-2x) = 160x - 2x^2 max revenue when r'=0, or x = 40 So, just plug that in as needed.
*November 9, 2014*

**Math 112**

not so. The value is a non-terminating decimal, so it cannot be written exactly. The calculator just shows the first few digits. The only way to write it exactly is: √3
*November 9, 2014*

**math**

14.1√2 = ?
*November 9, 2014*

**College Algebra**

27.95 + 0.15m = 45.95 find m
*November 9, 2014*

**Math**

how much in taxes? well, duh: 7% .07 * 43.99 = $3.08 so, add the price to the taxes to get the total
*November 9, 2014*

**Algebra**

If you mean 2/3y + 5 - 3 - 11/12y then collect like terms: 2/3 y - 11/12 y + 5-3 (2/3 - 11/12)y + 2 (8/12 - 11/12)y + 2 (-3/12)y + 2 -1/4 y + 2
*November 9, 2014*

**ap calc**

so, solve the equation for f'. You have 3sinx = -2cosx tanx = -2/3 So, that gives you x for maximum value of f(x). Just plug it in and evaluate f(x). Of course, you need to recall how to take sin(arctan(x)) and cos(arctan(x)) But that's just trig, right? Or, note that ...
*November 9, 2014*

**Can you check my answer - Physics**

clearly the net force is the sum of the downward and upward forces: -1.5N + 0.7N = -0.8N That is, 0.8N downward You just added the magnitudes, but did not take into account the directions
*November 9, 2014*

**math**

Not sure what your characters are, but (A∩B)∪C = {9,10}∪{11,13,15} = {9,10,11,13,15} (A∪B)∩C = {9,10,11,12,13,14}∩{11,13,15} = {11,13}
*November 9, 2014*

**ap calc**

f(x) = bx^2+6x if x <= 2 ax^3 if x>2 So, we have lim(x->2-) f(x) = 4b+12 lim(x->2+) f(x) = 8a That means we need 4b+12 = 8a Also, we need the derivatives to be equal: 2bx+6 -> 4b+6 3ax^2 -> 12a And they need to be equal: 4b+6 = 12a rearranging things a bit, ...
*November 9, 2014*

**Math**

Since y = kx, y/x = k That is, pick any two known values of x and y. Their ratio is the constant k.
*November 9, 2014*

**College algebra**

f(x) has 3 changes, so 3 or 1 + roots f(-x) has no sign changes, so no - roots check: http://www.wolframalpha.com/input/?i=6x^5-6x^4%2B7x^3-8
*November 9, 2014*

**consumer math**

799.99(1-0.40) = 479.99 or, $480
*November 9, 2014*

**calculus**

y = log |2-x| y' = 1/|2-x| (-1) = 1/(x-2)
*November 9, 2014*

**Pre-trig/Calc**

1 positive, 2 or 0 negative check: http://www.wolframalpha.com/input/?i=x^3%2B3x^2-18x-40
*November 9, 2014*

**Math**

start with x. The value after each step is listed below x 2x 2x+6 (2x+6)/2 = x+3 x+3-3 = x you always get your original number.
*November 9, 2014*

**calculus**

s = t^9 ln|t| s' = 9t^8 ln|t| + t^9/t = t^8(9ln|t| + 1)
*November 9, 2014*

**Math**

15.3g + 2q + 3.79 Note that you don't need an equation, just an expression
*November 9, 2014*

**calculus**

y' = (26x^2-26)e^-3x - 3(13x^2-26x+26)e^-3x = -13(3x^2-8x+8)e^-3x
*November 9, 2014*

**Math**

#1 False A triangle has three angles, which add up to 180 degrees. The two right angles use all that up. #2 True #3 True #4 False Just draw any obtuse triangle. If two of the legs happen to be equal, stretch one of them a little. #5 True #6 False. Draw a tall skinny isosceles ...
*November 9, 2014*

**Math -word problem**

Consider the room. The front wall is square ABCD, and the back wall is EFGH. The front outlet (P) is a foot from the floor (AB), and the back outlet (Q) is a foot from the ceiling (GH). A line directly up and across and down is 20 feet. But, you can do the following: Unfold ...
*November 9, 2014*

**calculus**

just use the product rule and chain rule: y = uv y' = u'v + uv' where u=(2x+1)^3 v=(4x+1)^-4 y' = 3(2x+1)^2(2)*(4x+1)^-4 + (2x+1)^3*(-4)(4x+1)^-5(4) = -2(2x+1)^2(4x+5) --------------------- (4x+1)^5
*November 9, 2014*

**math pre algebra**

how about 5x+7y
*November 9, 2014*

**Algebra 2**

plug in your coefficients at http://www.gregthatcher.com/Mathematics/GaussJordan.aspx to see all the details Or, you can try this: http://www.wolframalpha.com/input/?i=solve+{{3%2C4%2C1}%2C{1%2C3%2C-2}%2C{-2%2C1%2C-2}}*{{x}%2C{y}%2C{z}}%3D{{1}%2C{-2}%2C{-5}}
*November 9, 2014*

**Algebra 2**

(2x-1)^2 = x^2 + 33 4x^2-4x+1 = x^2+33 3x^2-4x-32 = 0 (3x+8)(x-4) = 0 ...
*November 9, 2014*

**math**

315 = 3^2 5 7 882 = 2 3^2 7^2 So, GCF = 3^2 7 = 63
*November 9, 2014*

**math count warm up**

just start writing down the facts. If the 4 digits, left to right are a,b,c,d, then: a+b=c b+c=d c+d=10a+b a+b=c d-b=c 10a+b-d=c a+b=d-b a+2b = d 10a+b-(a+2b) = a+b 8a = 2b b = 4a so, c=5a and, d=9a Since a,b,c,d are single digits, a must be 1. So, we get 1459
*November 9, 2014*

**algebra**

w(3w-2) = 16 w = 8/3 p = 2(8/3 + 6) = ?
*November 9, 2014*

**math**

6 - 4(2/3) = ?
*November 9, 2014*

**projectives**

time to hit: 4.9t^2 = 90 t = 4.29 s 4.29s * 50 m/s = 214.28 m
*November 9, 2014*

**calculus**

see related questions below
*November 9, 2014*

**Math**

Drop a perpendicular from G on CD to F. Now you have a rectangle GDEF with sides 3.5 and 4.5 Also, triangle CGF where CG = 3.5/√3 CF = 7.0/√3 Now the perimeter is easy - add up three sides of the rectangle, and the triangle.
*November 8, 2014*

**math**

I don't see any fractions If you meant (11+x)/(13+x) = 10/11 then x=9
*November 8, 2014*

**Calculus**

Do you mean ln√x or √lnx ?
*November 8, 2014*

**trig**

recall your sum of angles formula for tan recall that tan(180) = 0
*November 8, 2014*

**Math Question**

QR = 7.1 tan58° Area = (1/2)(PR)(QR)
*November 8, 2014*

**math**

your math is ok, freddy, but the spelling, not so much...
*November 8, 2014*

**math**

Hmmm. How can someone savvy enough to use a computer, not know what 1+1 is? I suspect either a test posting, or someone really bored.
*November 8, 2014*

**Algebra 2**

You always want to set things equal to zero: 6x^2-13x+6 = 0 Now, just have to have some practice factoring to get to (3x-2)(2x-3) = 0 Now, since if the product of two numbers is zero, one of the numbers must be zero. So, either 3x-2 = 0 and x = 2/3 or 2x-3 = 0 and x = 3/2 You ...
*November 8, 2014*

**Calculus (math)**

Draw a diagram, looking from the side. If the observer is at distance x, then The angle Ø from the eye to the bottom of the picture is such that tanØ = d/x The angle θ subtending the picture is tan(Ø+θ) = (d+h)/x We want to determine x for ...
*November 8, 2014*

**math**

(3x-2)/8 + (2-x)/ 4 = - 1/2 easy way: clear fractions by multiplying by 8: (3x-2) + 2(2-x) = (-1/2)(4) 3x-2+4-2x = -2 x+2 = -2 x = -6 check: (3(-6)-2)/8 + (2-(-6))/4 = -20/8 + 8/4 = -5/2 + 2 = -1/2
*November 8, 2014*

**mathematics**

a + a+2d = 12 (a)(a+d) = 24 a=4, d=2 check: 4,6,8,10,... 4+8=12 4*6=24
*November 8, 2014*

**Mustapha**

ever try google? Here's one discussion: http://www.meritnation.com/ask-answer/question/determine-the-oxidation-number-of-cr-in-k2cr2o7/redox-reactions/1515787
*November 8, 2014*

**algebra**

#1 If you mean f(n) = 3(n-3) then f(5) = 3(5-3) = 6 f(n) = 3^(n-3) then f(5) = 3^2 = 9 f(n) = 3^n - 3 then f(5) = 3^5-3 = 240 How did you come up with 279? #2 f(n) = 2f(n-1)+2 f(1) = 4 f(2) = 2(4)+2 = 10 f(3) = 2(10)+2 = 22 #3 f(n) = (4-n)/(n+3) f(3) = (4-3)/(3+3) = 1/6 #4 I ...
*November 8, 2014*

**Maths**

C = pi * d so, the turns is 44/C where C is in meters
*November 8, 2014*

**math - typo**

3:1:15 requires three quantities.
*November 8, 2014*

**calculus**

d/dx u^n = nu^(n-1) u' d/dx arctan(u) = 1/(1+u^2) u' d/dx ln(u) = 1/u u' So, we have y' = 2(3/2) √(22x+31) * (22) + 1/(1+(22x+21)) * (1/2) * 1/√(22x+21) * 22 + 1/(11x+16) * 11 - 22 = 66/√(22x+31) + 11/((22x+22)√(22x+21)) + 11/(11x+16) - 22
*November 8, 2014*

**calculus**

That would be 4(cos(6x-1) - 6xsin(6x-1)) ------------------------------ 3cos(3x) - 3 at x=0 that is 4(cos(-1)-0) ---------------- 3-3 -> -∞
*November 8, 2014*

**Calculus**

See the related questions below
*November 8, 2014*

**Trig**

Extend AB to meet the vertical from C at D. It is easy to determine that in triangle ABC ∠C = 47° ∠B = 88° Now just use the law of sines to get AB.
*November 8, 2014*

**Intermediate Algebra**

well, let's just assume that there is a t. After all, if there is none, the B is just a constant: 604.47 So, since polynomials are normally written in descending power order, I'd guess B = 18.75t + 585.72 So, you want to solve 18.75t + 585.72 > 1050 18.75t > 464....
*November 8, 2014*

**Intermediate Algebra**

B=18.75+585.72 where is the t?
*November 8, 2014*

**Calculus (math)**

See the related questions below
*November 8, 2014*

**Math**

cos is negative in QII, QIII You reference angle is 0.927 So, x = pi±0.927
*November 8, 2014*

**calculus**

V = IR dV/dt = R dI/dt + I dR/dt Now just plug in your numbers.
*November 8, 2014*

**Calculus**

I guess you should have checked my math. The actual formula for the volume is (π/3)((18+y)(3+y/6)^2-18*3^2) = π(y^3/108 + y^2/2 + 9y) because the water is in the bottom of the cone dv/dt = π/36(y+18)^2 dy/dt 4.9 = π/36*20^2 dy/dt dy/dt = .14 m/min or 14.0 ...
*November 7, 2014*

**Calculus**

When the water has depth y, the radius of the surface is 3 + (y/12)(5-3) = 3 + y/6 Its volume at that point is v = 1/3 (R^2-r^2) h = (1/3)((3+y/6)^2-3^2)y = y^3/108 + y^2/3 Now we are ready to begin. When y=2, v = 8/108 + 4/3 = 38/27 dv/dt = (y^2/36 + 2y/3) dy/dt 4.9 = (4/36...
*November 7, 2014*

**Calculus (math)**

as usual, draw a diagram. The distance z between the boats at time t hrs after 2:00 is z^2 = (15t)^2 + (20-20t)^2 2z dz/dt = 2(15t)(15) + 2(20-20t)(-20) z dz/dt = 1250t - 800 clearly dz/dt=0 when t=8/1250 hours Now just change that to a time of day.
*November 7, 2014*

**AP CALC. AB**

the .75 comes from the fact that the diameter is increasing 1t 1.5in/min. The radius is half that. and yes, he meant to solve for dh/dt, since that was the question asked. Part 1 just uses the fact that the volume of a box is length*width*height. can you say duh?
*November 7, 2014*

**helpppppppp**

7c+3d = 4m 1m = 1c+1d So, 4m = 4c+4d 7c+3d = 4c+4d 3c = d
*November 7, 2014*

**BRAINMATH**

If the family has b boys and g girls, b = g+4 So, b = (g-1)+5 so, each sister has 5 more brothers than sisters
*November 7, 2014*

**Pre-Calc/Trig**

numerator will be 1 or 2 denominator will be 1 or 3 all can be positive or negative
*November 7, 2014*

**Math**

cos pi/3 = 1/2 so, t = pi/3 That's the reference angle. cos is positive in QI and QIV, so the other solution is t = 2pi - pi/3
*November 7, 2014*

**Physics**

the vertical speed is 200 sin30 = 100 m/s So, the height is h(t) = 100t - 4.9t^2 As you recall from algebra I, the vertex of the parabola is at t = -b/2a, which in this case is 100/9.8 So, plug that in to get the max height. The ball is in the air twice that long, and you know...
*November 7, 2014*

**Algebra**

I'll do one, and you try the other. 2x^2+7x = 4 (x^2 + 7/2 x) = 2 (x^2 + 7/2 x + (7/4)^2) = 2 + (7/4)^2 (x + 7/4)^2 = 81/16 x + 7/4 = ±9/4 x = -7/4 ± 9/4 x = -4 or 1/2 Just recall that (x+a)^2 = x^2 + 2ax + a^2 That's why I added (7/4)^2 to both sides. ...
*November 7, 2014*

**science Help 911!!**

Looks good to me.
*November 7, 2014*

**ALakh narayan sing high school Ekma saran**

1/6(2x+3y)+x/3=8 1/2(7y-3x)-y=11 Rearranging things a bit to get rid of the bothersome fractions, we have 4x+3y = 48 -3x+5y = 22 Since y = (48-4x)/3, -3x+5(48-4x)/3 = 22 Or, -9x+240-20x = 66 29x = 174 x = 6 Now you can easily find y.
*November 7, 2014*

**algebra - incomplete**

I think you are missing a t in the formula.
*November 7, 2014*

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