Wednesday
August 20, 2014

Posts by Steve


Total # Posts: 24,330

math
If those "x" signs mean multiplication, then you surely know that 0x anything is zero.
June 18, 2014

math
n(n-1)/2 = 171 Since 342 = 18*19, there were 19 teachers.
June 18, 2014

physics
g = GM/r^2 at r+h, g1 = GM/(r+h)^2 at r-x, g2 = GM/(r-x)62 ∆g = GM(1/(r-x)^2 - 1/(r+h)^2) = GM/((r-x)^2(r+h)^2) ((r+h)^2-(r-x)^2) = GM/((r-x)^2(r+h)^2) (2rh+h^2 - 2rx+x^2) Since r-x and r+h are both approximately r, we have ∆g = GM/r^4 (2r(h-x) + h^2+r^2) = 2GM/r^3...
June 18, 2014

finite mate
anythingP0 = 1 There is only 1 way to choose nothing.
June 17, 2014

Algebra
You can factor out a^2 b, giving a^2 b (a^2 + b^2) Not sure that's any simpler.
June 17, 2014

Math
multiply RS top and bottom by cos2x and you have 2/(1-cos2x) = 2/(1-(cos^2 x - sin^2 x)) = 2/(1-cos^2 x + sin^2x) = 2/(2sin^2 x) = 1/sin^2 x = csc^2 x
June 17, 2014

Algebra
you want two factors of 45 which add to 18. Since 45 = 15*3, you get (x+15)(z+3)
June 17, 2014

math
y = 6x+4 Since you know the number of games, and the cost depends on that, x is the independent variable.
June 17, 2014

math
Arrange the coefficients into a 3x3 matrix, filling in zeros for missing values. A matrix is in row echelon form if (1) All nonzero rows (rows with at least one nonzero element) are above any rows of all zeroes (if any). (2) The leading coefficient of a nonzero row is always ...
June 17, 2014

Algebra/please can some one help I forgot
Just look up the formula for monthly payment of loan amortization, and plug in your numbers.
June 17, 2014

MATH
no problem. Literally -- no problem. All you have done is give us the definition of some set of BOYs.
June 17, 2014

geometry
C = 3.14 * 60 = 188.4 cm 33.3 rpm means the bicycle travels 33.3 * 188.4 cm in one minute.
June 17, 2014

geometry
360 degrees is just one revolution. So, in 48 minutes, it turns 48 times. By the way, most LPs rotate at 33 1/3 rpm, not just 1 rpm. Also, they don't play for any 48 minutes either. Stupid question.
June 17, 2014

geometry - oops
I misread 1008 as 1080. Go with Reiny.
June 17, 2014

geometry
720 = 2^4 * 3^2 * 5 1080 = 2^3 * 3^3 * 5 672 = 2^5 * 3 * 7 So, the largest number that evenly divides all of those is 2^3 * 3 = 24
June 17, 2014

algebra
x+y=15 8x+5y=96 now just solve for x and y
June 17, 2014

Math
150 is less than the mean for Natalia's class. So, if that score is removed, the mean rises. Similarly, since 150 is greater than the mean for Eric's class, if that score is added, the mean rises.
June 17, 2014

Math
y = x^2 + 3x + 1/4 = x^2 + 3x + (3/2)^2 + 1/4 - (3/2)^2 = (x + 3/2)^2 - 2 That should answer most of your questions.
June 17, 2014

Math
30x+20y+10z = 800000 x+y+z = 40000 x = y/2 x=10,000 y=20,000 z=10,000
June 17, 2014

algebra 1
If we model the situation as y = mx+b then we have 120m+b = 18 300m+b = 6 Subtract to get -180m = 12 m = -1/15 So, b = 26 y = -1/15 x + 26 y=0 when x = 390
June 17, 2014

finite math
Hmm. Looks like 0.438
June 17, 2014

finite math - PS
That's the experimental probability. The theoretical probability is still 1/2.
June 17, 2014

finite math (probability
I'd say 57/100
June 17, 2014

math
400m+b = 2150 300m+b = 1650 subtract to get 100m = 500 m = 5 so, b = 150 y = 5x+150
June 17, 2014

physics
given the drawing as shown below, I calculate 3.62 km at 46°
June 17, 2014

geometry
Assuming the chords are parallel, think of 8-15-17 right triangles.
June 17, 2014

Science
Seems to me that the only possible reason can be that ice provides less friction, whatever the underlying properties. Friction translates into a restraining force, reducing the speed.
June 17, 2014

science
F = ma, so 20 = 4m m = 5 kg
June 17, 2014

math
what a lot of noise. Distance traveled: 128100 ft = 24.26 mi Average speed: 335.92 mi/hr so, time falling is 24.26mi / 335.92mi/hr = 0.0722hr = 4.3 minutes
June 17, 2014

chemistry
1000cm^3 * 13.6g/cm^3 * 1mole/200.59g = 67.8 moles
June 17, 2014

chemistry
.09g * 1mole/18g * 6.02*10^23mol/mole = 3.01*10^21 molecules
June 17, 2014

chemistry
just plug in the mol wts of the compounds in 0.78*N2 + 0.21*O2 + 0.009*Ar * 0.001*CO2
June 17, 2014

algebra
the ratio is 6:6, making 12 total. 48 = 12*4, so 24:24 will satisfy everyone.
June 17, 2014

Geometry
figure the length and slope of AB and CD. If they match, it's a ||-ogram.
June 16, 2014

Geometry
well, what are the diagonals? AC and BD midpoint of AC = (-1/2,-2) midpoint of BD = (-1/2,-2) Looks like the diagonals bisect each other.
June 16, 2014

projectile motion
we know that the path follows x(t) = v cosθ t y(t) = 160 + v sinθ t - 4.9t^2 I will assume that the cliff and the tower are the same, otherwise I'm confused. x(20) = 1800 y(20) = 0 So, 20v cosθ = 1800 20v sinθ = 1800 Clearly θ = π/4 and v = ...
June 16, 2014

Algebra
no solution the lines are parallel, and so do not intersect.
June 16, 2014

Algebra
see the solution at http://www.wolframalpha.com/input/?i=solve+4y%3Dx%2B4%2C+x%3D2%2F3y%2B8%2F3+
June 16, 2014

Physics
150km/2.5hr = 60km/hr 150km/2.0hr = 75km/hr velocities is the same, but directed. 300km/4.5hr = 66.67km/hr avg velocity is 0, since no net distance was traveled.
June 16, 2014

Physics
4 hr * 300km/hr = 1200km 2.5 hr * 400km/hr = 1000km 2200km/6.5hr = 338.46km/hr
June 16, 2014

Math: Trig
since cos pi/3 = 1/2, sec pi/3 = 2 But, arcsec has principal values from 0 to pi, so arcsec(-2) = pi - pi/3 = 2pi/3. Note: Some authors define the range of arcsecant to be ( 0 ≤ x < π/2 or π ≤ x < 3π/2 ), because the tangent function is ...
June 16, 2014

MATH
No idea. Do it the way I did, but you have to use integration by parts. If you get stuck, show how far you got. You should wind up with -(x+1)e^-x for x<0 (x-1)e^x for x>=0
June 16, 2014

MATH
since |x| = -x for x < 0. ∫[-∞,x] e^-|t| dt = ∫[-∞,x] e^t dt if x < 0 = e^t So, for x>=0, ∫[-∞,x] e^-|t| dt = ∫[-∞,0] e^t dt + ∫[0,x] e^-t dt = 1 + (1-e^-x) = 2 - e^-x
June 16, 2014

maths
32 is 2^5 so, 1/32 = 1/2^5 = 2^-5
June 16, 2014

Math - incomplete
did you want some particular value for x?
June 16, 2014

Calculus
Note that you have ∫1/(x^2 − 2x + 8)^(3/2) dx = ∫1/((x-1)^2 + 7)^(3/2) dx If x-1 = √7 tanu (x-1)^2 + 7 = 7 sec^2 u dx = √7 sec^2 u du and you have ∫1/(√7 secu)^3 * √7 sec^2 u du = ∫ 1/7 cosu du = 1/7 sinu = 1/(7 csc u) = 1...
June 16, 2014

pseudocode app
this kind of code is about as simple as it gets. I don't know what language you plan to use, but do a little google to see how others have performed the operations you desire. There are lots of code snippets on line.
June 16, 2014

pseudocode app
read price tax = price * 0.08 print price,tax
June 16, 2014

Dela ray Mkhatshwa j.s.s
Let AC and BD intersect at E. Note that AE = 3 Draw a vertical line which will contain AC. Mark point E by intersecting an arc of radius 3 from A to E. Construct the perpendicular at E to AC. That will contain BD. Draw an arc centered at A of radius 6, which will intersect the...
June 16, 2014

Arithmetic
since the ratio between terms is constant, (k+6)/(2k+3) = k/(k+6) (k+6)^2 = k(2k+3) k^2+12k+36 = 2k^2+3k k^2 - 9k - 36 = 0 (k-12)(k+3) = 0 k = 12 and the sequence is 27,18,12,... so the ratio is 2/3 and S = 27/(1/3) = 81
June 16, 2014

Science
you need 4m = 600
June 16, 2014

sci
ever been on a roller coaster? ever stuck your finger in a wall outlet?
June 16, 2014

algebra
If the larger monitor has width w, then its length is w+5. So, we have w(w+5)-80 = 70 w^2 + 5w - 150 = 0 (w+15)(w-10) = 0 ...
June 16, 2014

Math
or, you can avoid b altogether and go straight to the point-slope form of the line with slope 1/2: y-12 = 1/2 (x-10)
June 16, 2014

physics
total distance is 30m + 40m = 60m = 6000cm total time is 5s + 20*60s = 1205s avg speed is thus 6000/1205 = 4.98cm/s
June 16, 2014

science
Look, I'm Furiously Engaged!
June 16, 2014

Chemistry
Since the reaction is 2HNO3 + Ba(OH)2 -> Ba(NO3)2 + 2H2O It takes 2 moles of HNO3 to neutralize 1 mole of Ba(OH2) 2.5g Ba(OH)2 is 0.0146 moles So, you need 0.0292 moles of HNO3 0.0292M / 0.109M/L = 0.268L of acid.
June 16, 2014

maths
since θ is in QII and Ø is in QIII, tanθ = 3/-4 secØ = √5/-2 now go figure.
June 16, 2014

physics please help!!!!!!
You want to find where 30t - 4.9t^2 = 60 - 4.9(t-.5)^2 t = 2.34 now plug that in to find either height. Assuming you meant 60m above where the first mass started. Things are different if the second mass is dropped when the first mass is 60m below it. But I'm sure you can ...
June 16, 2014

Calculus
Your function becomes less unwieldy if you note that if you divide top and bottom by cosx, you have y = (1/2 sin2x)/(sinx+cosx) All those nasty sec^2 and stuff go away and you have 2nd: wolframalpha.com is your friend. Enter 2nd derivative sinx/(1+tanx) and it pops right up. ...
June 16, 2014

Calculus
From what I can decipher from your cryptic use use of arcana (like A, II DC, Nr, etc.) your reasoning appears sound. I have a bit of trouble distinguishing between II DC and second DC. If they are the same, how can you check the sign of second DC without calculating it? If y&#...
June 16, 2014

physics
depends on the size of the umbrella.
June 16, 2014

math
The height y(t) is given by y(t) = h + vt - 16t^2 h + v - 16 = 148 h + 2v - 64 = 272 So, h=-8 v=172 y(t) = -8 + 172t - 16t^2 y(6) = 448
June 16, 2014

algebra
Since the population grew by a factor of 1.64 over 8 years, we have p = 4.2 * 1.64^(t/8) Since 1.64 = e^0.49 (call it e^.5), we have p = 4.2 * e^(t/16)
June 15, 2014

math
23% of wages is 14204.80 SS tax is 7658.24 FICA tax is 1791.04 so, subtract all those from her gross. Or, note that the total taxes add up to 38.3%, so just subtract that amount. Or not. You never really did ask a question.
June 15, 2014

Precalc
An equation is not a function. However, the definition of a function is usually written as an equation, as in f(x) = 2e^x - 7 But, that's really just a definition. An equation is usually something you have to solve for a particular value. For example, you might have to ...
June 15, 2014

calculus
Oops. The w(t) given above is the y-value of Janice's position. You also need to use the x-value, which I'm sure you can do.
June 15, 2014

calculus
If Janice is at (0,0) when t=0, then the wheel obeys w(t) = 20(1-cos(π/8 t)) The ball follows the parametric equations x(t) = -70 + 60cos60° t y(t) = 60sin60° t - 16t^2 I have no idea where point A is, but having the equations should make things amenable to solution.
June 15, 2014

maths
(x+y)/2 = 44 If x=12, then (12+y)/2 = 44 12+y = 88 y = 76
June 15, 2014

Algebra
we have x^2-2 where x <= 1 2x where x < 1 Not quite clear where you want to go with this. I suspect you really meant 2x where x < 1 x^2-2 where x >= 1 If so, then the graph is a line which stops at x=1, and a parabola from there on. There is a jump discontinuity at...
June 15, 2014

bearing and distance
Use the law of cosines. After t hours, the distance d between the vehicles is d^2 = (8t)^2 + (5t)^2 - 2(8t)(5t)cos70° because the angle between the bearings if 25+45 = 70° So, just plug in t=3 and solve for d. As for the bearing from q to p, just find the slope of the ...
June 14, 2014

math,bearing and distance
not sure what bearing "s30 degree of north" is.
June 14, 2014

Math
you can easily see that K = 18-C So, put that into the 2nd equation and you have 2(18-C)+4C = 50 36-2C+4C = 50 2C = 14 C = 7 So, K = 11
June 14, 2014

math
x^3+3x = x(x^2+3) = (a^2/3-a^-2/3)((a^2/3-a^-2/3)^2+3) = (a^2/3-a^-2/3)(a^4/3 + 1 + a^-4/3) Note we have the factorization of the difference of two cubes: = a^2 - a^-2
June 14, 2014

Another this math tho
ding ding -- we have a winner!
June 13, 2014

this math tho
well, does 3(-10)+54 = 18?
June 13, 2014

3 questions Math
Oops. The synthetic division site was http://www.mathportal.org/calculators/polynomials-solvers/synthetic-division-calculator.php
June 13, 2014

3 questions Math
#18 - did you try this at the syntehtic division site I gave you? You can see polynomial long division at calc101.com; click on the "long division" button. #19 If you meant 1/(2x + 14) - 9/(x + 7) = -6 then that's just 1/(2x+14) - 18/(2x+14) = -6 -17/(2x+14) = -6...
June 13, 2014

Algebra ll
take a visit to http://www.mathportal.org/calculators/polynomials-solvers/synthetic-division-calculator.php and enter your coefficients. It will show the calculation, and even explain it if needed. It's hard to do it here, due to browser formatting of html.
June 13, 2014

Algebra
just find when the two are equal: 16x+150 = -x^2+60x-10 x^2 - 44x + 160 = 0 (x-40)(x-4) = 0 Now the answer should be clear.
June 13, 2014

algerbra
try something like this: http://www.wolframalpha.com/input/?i=3x%2By+%3C%3D+5 you can type in many different things, and it will show you the solution
June 13, 2014

algebra 2
B(t) rose by 32
June 13, 2014

Algebra (Factoring)
2(x^4-5x^2-36) 2(x^2+4)(x^2-9) 2(x^2+4)(x-3)(x+3)
June 13, 2014

Algebra
x/5 = 40/1.6 x/150 = 1.6/40 solve for x
June 13, 2014

Math
99 action means 55 horror, for a total of 154 films in 7 days. That's 22 films/day on average.
June 13, 2014

geometry
Assuming the sun rises at 6 am and sets at 6 pm, then at 9 am it is 45° above the horizon. That means a 147cm person will cast a 147cm shadow.
June 13, 2014

science
total mass of H2SO4 is 98 So, figure the % mass of each of the elements: H2 = 2 S = 32 O4 = 64
June 13, 2014

Math
since √x is not real for x < 0, we need 5y+1 >= 0 y >= -1/5 3y-5 >= 0 y >= 5/3 So, we need y >= 5/3 for the domain Now proceed to solve: √(5y+1) - √(3y-5) = 2 5y+1 - 2√[(5y+1)(3y-5)] + 3y-5 = 4 8y - 8 = 2√[(5y+1)(3y-5)] (4y-4)^2...
June 12, 2014

maths
This is just a work problem in disguise. Together the cars must cover a distance. 1/x = 1/4 + 1/6 = 5/12 x = 12/5 Check. Say the distance is 120 miles In 2.4 hours, the car covers 2.4/4 = 0.6 the distance. In 2.4 hours, the van covers 2.4/6 = .4 the distance. ok
June 12, 2014

math
you can order n things in n! ways. 24! = 6.2 * 10^23
June 12, 2014

Math
v = pi r^2 h So, just plug in r=3.7m and h = 2.4m
June 12, 2014

MATH
as you know, the derivative of e^u = e^u u' So, ∫e^u du = e^u Here, u = -x, so du = -dx You thus have ∫e^u (-du) = -∫e^u du = -e^u = -e^-x
June 12, 2014

Algebra
no way to tell
June 12, 2014

Algebra
If the first takes x hours, 1/x + 1/(x+5) + 1/(3x) = 1/(9/4) x = 4 So, the 3 pipes require 4,9,12 hours.
June 12, 2014

Arithmetic
1/3 of the marbles are green. So, 1/3 of at least 54 are green. How many is that?
June 12, 2014

whole number
1219 - 32 - 24 = ?
June 12, 2014

Science(electric circuits)
hmmm. The current in each parallel path may be different. That's a pretty open question, with no context.
June 12, 2014

englewood
total income,state,city tax is 6% 6% of 215 = 12.90 So, total deductions are 15.16+29.33+12.90 = 57.39 Net income is thus 215.00-57.39 = $157.61 Who says we are not taxed enough?
June 12, 2014

science-chemistry
.00565*450 = 2.54g of NaCl So, how many moles is that?
June 12, 2014

Math
I'm having a little trouble visualizing the angles in question. If we label the boats A and B and the dock D, which angles are we talking about?
June 12, 2014

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