Thursday
August 21, 2014

Posts by steve


Total # Posts: 24,357

math - oops
Oops. N=13
July 17, 2014

math
Since 17 is prime, N=1
July 17, 2014

math
using the well-known proofs that sinx -> x, we can conclude that tan2x -> 2x so we have the limit as (2x-x)/(3x-x) = 1/2
July 17, 2014

Grammar
If a shark ate the fish, then, yes, the fish got eaten by a shark. Past tense. However, "gets" can be ok, too. Maybe you are talking about what happens when a fish is near a shark. If the shark is hungry, then what usually happens is that the fish gets eaten by the ...
July 17, 2014

intermediate Algebra
m = y-7 1/m + 1/y = 1/12 1/(y-7) + 1/y = 1/12 y = 28 so, m = 21 check: working together, in one day they can assemble 1/28 + 1/21 = 1/12 of the whole.
July 17, 2014

intermediate Algebra
1/2 - 1/4 = 1/x x = 4 Check: water comes in at 1/2 sink/minute water drains out at 1/4 sink/minute net flow: 1/2-1/4 = 1/4 sink/min So, it takes 4 minutes to fill the sink
July 17, 2014

analytic geometry
AB has slope 2 and length √5 mid(AC) = (-1/2,1/2) mid(BC) = (-1,-1/2) so that segment has slope 2 and length √5/2
July 16, 2014

geometry
(2,1)+(1,4) = (3,5) (5,2)+(1,4) = (6,6) So, true
July 16, 2014

geometry
just apply your distance formula. Plot the two points, and join them in a right triangle with legs parallel to the axes; the hypotenuse is the line joining the points.
July 16, 2014

geometry
pick the pair with (x,y) and (-x,-y)
July 16, 2014

math
total area = 18*8 = 144 picture area = 14*4 = 56 so, just subtract to get the frame only
July 16, 2014

calculus
dN/dt = 528e^0.4t / (11+e^0.4t)^2 Now just plug in t=4
July 16, 2014

calculus
Do you mean to divide? N(t) = 650/(1+649e^-.5t) What's the trouble? Straightforward evaluation of N or solving for t. That's just algebra. If I have the function right, its graphs is http://www.wolframalpha.com/input/?i=650%2F%281%2B649e^%28-.5t%29%29
July 16, 2014

Math
simple: p(x) = r(x) - c(x)
July 16, 2014

nau
John's idea is interesting, but leaves you no closer to the solution. 4x+y=21 7x-4y=8 Consider his multiplication idea, and work it this way: 28x+7y = 147 28x-16y = 32 Now subtract to get 23y = 115 y = 5 now you can find x easily. The other set is even simpler. You know ...
July 16, 2014

math
and then subtract the 18 minutes already walked. Or, consider that there is 1/4 of the way to go. That is 1/3 as far as he's already gone, so it will take 1/3 as long to walk it. That is, 6 more minutes.
July 16, 2014

math
yes. care to proofread your posting and rephrase the question?
July 16, 2014

math
(12*87+18x)/(12+18) = 90 Now just solve for x
July 16, 2014

statistics
what, you cannot list the samples of size 3? ABC ABD ABE ...
July 16, 2014

Math - clarify
Hmmm. What does "list price of $100 less 7%, and 6%" mean? Two successive discounts? Also, after all the explanation, I don't see an actual question? What is it you are trying to calculate?
July 16, 2014

Math
I think it's a divisibility problem, where she meant If a|(b-2c) and a|(2b+3c) the a|b and a|c.
July 16, 2014

algebra
If there are s students, a adults, and g geezers, then s+a+g = 400 8s+10a+7g = 3535 a = s+g-10 Now just solve for the numbers
July 16, 2014

calculus
did you check out the hints I gave on your previous post of this problem? If so, where do you get stuck? The ticket problem is similar. How far do you get on that one?
July 16, 2014

maths
25^2 = 625
July 16, 2014

Math (Discrete Math)
271 is prime, so N is a multiple of 271 2014 = 2*19*53, If N = 271*2*2014, GCD(N,2014) = 2*271 and GCD(N,271) = 271 So, it appears to me that 271*2*2014 is the smallest N that fits the requirements
July 16, 2014

math
since the ratio of height-to-shadow is the same for both objects, h/29,2 = 3,5/5,2 Now just solve for h.
July 16, 2014

Math
well, that would naturally be 0.02 * 5270
July 16, 2014

mathematics
the figure is really just a sphere of radius r and a cylinder of radius r and height 4r. So, the volume is V = 4/3 π r^3 + πr^2 (4r) = 16/3 π r^3 So, dV/dt = 16πr^2 dr/dt That means that dr dt = dV/dt / (16πr^2) The surface area is A = 4πr^2 + 2&#...
July 16, 2014

Math Help
just list the digits as given, moving the decimal point 9 places to the right, adding zeroes as needed.
July 15, 2014

Calculus Help
the domain is 260 <= x <= 410 the price per chair is 88.00 - 0.02(x-260) revenue is price * quantity, so R(x) = x(88.00-.02(x-260)) = 93.2x - .02x^2 For maximum revenue, just find the vertex of the parabola. For minimum, figure the revenue at the two ends of the domain, ...
July 15, 2014

Calculus Help
revenue is price * quantity, so R(q) = 551q profit is revenue minus cost, so P(q) = 551q - (q^3-60q^2+1200q+760) You should probably graph P(q) to find the max. Take a look here: http://www.wolframalpha.com/input/?i=551q+-+%28q^3-60q^2%2B1200q%2B760%29 If you have calculus as ...
July 15, 2014

Calculus Help
profit P(q) = R(q)-C(q), so P(q) = 510q - (9400+3q^2) dP/dq = 510 - 6p P is maximized when dP/dq = 0, so ...
July 15, 2014

maine s
well, 500 is 25% of 2000, so ...
July 15, 2014

trig
Just review the definitions of the basic trig functions. Check the diagram, and you can see that the height h can be found using h/220 = sin 36°
July 15, 2014

Lisa
your answer looks correct to me. There must have been a typo in the problem, with a spurious "root" tossed in.
July 15, 2014

math
assuming that "no students of school A and B would get mixed up" means that each row contains only students from one school, let's find the largest number that divides both 336 and 432. GCF(336,432) = 48 So, school A has 7 rows of 48 and school B has 9 rows of 48
July 15, 2014

drivers' ed.
Judging from your experience, I would have to say, YES!
July 15, 2014

Algebra
since your speed is 5 km/hr, all the distances must be multiples of 5, since you start counting at the fountain. Or, if the somewhat vague description means that you want the total distance covered, starting at the fountain, then you have to start with 2, and after that, all ...
July 15, 2014

physics
how about ÿ ok
July 15, 2014

physics
i mean #&255; ok
July 15, 2014

physics
finally #&255 ok
July 15, 2014

physics
and also ẏ ok
July 15, 2014

physics
i mean ẍ ok
July 15, 2014

physics
i also get Ẍ ok
July 15, 2014

physics
i get ẋ ok
July 15, 2014

math
An equilateral triangle of side s has area √3/2 s^2 You have four triangles of side 8.
July 15, 2014

math
the slope of the line is (-4-2)/(1+2) = -2 So, use the point-slope form of the line, using either of the given points.
July 15, 2014

maths
Since time = distance/speed, 1.5/(8-s) + 1.5/(8+s) = 0.4 s = 2
July 15, 2014

math (help please)
review your "standard angles." sin π/3 = √3/2 sine is negative in QIII and QIV. That means that sin(π+π/3) = sin(2π-π/3) = -√3/2 Now you can add any multiple of 2π to those values, and you get all real numbers as required. If...
July 14, 2014

math
Recall that if A takes A hours, and B takes B hours, 1/A + 1/B = 1/2 So, if B does the task in x hours, A takes x+3 hours: 1/(x+3) + 1/x = 1/2 Now just solve for x.
July 14, 2014

math
Assuming you meant √(x-6)=√3-√x, we square both sides and get x-6 = 3-2√(3x)+x -9 = -2√(3x) 9/2 = √(3x) 81/4 = 3x x = 27/4 Check: √(3/4) = √3-√(27/4) √3/2 = √3(1-3/2) √3/2 = -√3/2 Nope. If you meant...
July 14, 2014

Algebra
decaying to 10% takes log0.10/log0.5 = 3.32 half-lives So, A's half-life is 33/3.32 = 9.94 days B's half-life is 43/3.32 = 12.95 days Looks like (a) is the answer
July 14, 2014

math
each line describes the previous line. So, the next line is 311211 BTW, the last entry in your post should have been 111221, making the real next line 312211
July 14, 2014

Math
Draw the triangle. One leg is 1, and the hypotenuse is 4. So, the other leg is √15 the cosine of the angle is √15/4
July 14, 2014

Differential Equations
(x^2+1)dx + x^2y^2dy=0 x^2y^2 dy = -(x^2+1) dx y^2 dy = -(x^2+1)/x^2 dx 1/3 y^3 = -x + 1/x + C ...
July 14, 2014

Algebra
log0.900.6 - log0.850.6 = 1.7 or, since you probably don't have a button for log0.9x, log(0.6)/log(0.9) - log(0.6)/log(0.85) or even log(0.6)(1/log(0.9)-1/log(0.85))
July 14, 2014

Geometry
I didn't see where the solid was a pyramid. Usually a prism is a right prism, so the v = (area of base)*height
July 14, 2014

science
Name it analogously with table salt, which is Sodium Chloride. That -ide suffix indicates that there are just the two elements. Ever heard of the ointment Zinc Oxide? Same deal.
July 14, 2014

math
the x-coordinate is halfway between the two end x-values: (-3 + -8)/2 = -11/2 Do the y-value the same way.
July 14, 2014

math
after n cuts, the thickness is 0.1 * 2^n mm. so, evaluate when n=30.
July 14, 2014

algebra
just solve for t when the height is zero: -16t^2 + 112t + 128 = 0 just a normal quadratic equation.
July 14, 2014

Alegbra
how many times is this going to be posted? Review the point-slope form of a line: a line with slope m, through the point (h,k) has the equation y-k = m(x-h) So, look at the equation above, and read off m and (h,k)
July 14, 2014

Alegbra
The point is clearly (-5,4) Now since the slope is 3/2, a second point is up 3 and right 2.
July 14, 2014

Trigonometry
just figure s(5)-s(1)
July 14, 2014

physics
The tank weighs the same, regardless of its contents. Figure the volume of material, and multiply that by the material's density. :-)
July 14, 2014

physics
figure the volume: .18 * .78 * .44 m^3 now multiply that by the density, in kg/m^3
July 14, 2014

Pre algebra
(5*62 + 50)/6
July 14, 2014

math
let the numbers be x-1,x,x+1 The sum is 3x = 39 so, the middle number is 13
July 14, 2014

Math
log740353607 = log40353607/log7 = 9 so, 40353607 = 7^9
July 14, 2014

math
x = 2^(1/2) since log √x = 1/2 log x, log x = -2 x = 10^-2 lnx = ln(e*(x+1)) x = e*(x+1) ...
July 14, 2014

Physic
1W = 1J/s 1 kwh = 1000 Wh = 1000J/s * 3600s/h
July 14, 2014

Math
(9+1)/(9+1+6)
July 14, 2014

physics
750 + 750 + 625
July 14, 2014

Calculus 2
actually, the integral isn't so bad if you recognize that the integrand is just x^4 + 1/x^4 http://www.wolframalpha.com/input/?i=arc+length+of+x^5%2F10%2B1%2F%286x^3%29+from+3+to+6
July 14, 2014

Physics
well, you have the mass of 1 liter. So, what is the mass of 2 liters? Now just look up the conversion factor for kg to lb. A handy site is http://www.onlineconversion.com/weight_common.htm On the home page there, you can find many other conversion calculators.
July 14, 2014

mqr/117
rewrite f(x) as 5(x + 3/10)^2 + 11/20 and then you can just read off the coordinates of the vertex.
July 13, 2014

Math
you want the set of elements common to your two sets. So, which numbers are in both lists?
July 13, 2014

Math
The number of people taking something is 23+32-9 So, that leaves how many taking nothing?
July 13, 2014

Alegbra
They are perpendicular if the product of their slopes is -1. So, is (-7)(-7) = -1 ?
July 13, 2014

Math
think of the calendar as units of 24 hours So, 5:44 am on day 10 is the same as 29:44 on day 9. So, subtract 14 from 29 and you have 15:44 of the previous day, or 3:44 pm. Or, you could just subtract 24 hours, giving you 5:44 am of the previous day. But you only wanted to ...
July 13, 2014

Alegbra
If you mean y = -3/2 (x+5) you can see easily that y=0 when x = -5. So, that's where the graph crosses the x-axis. Now, since the slope -s -3/2, just mark a second point, 3 down and 2 to the right from there. Join those two points with a line, and that's the graph.
July 13, 2014

math
I'd say that would be 17+3=20 assuming the ladder is laid vertically against the wall -- an unusual placement, to be sure.
July 13, 2014

math
the grade would be 15/5280 = 0.284%
July 13, 2014

Math 221
as with most problems involving fractions, work first with the denominators. They cannot be added or subtracted unless they all have the same denominator. 5/12 + 7/9 The GCD(12,9) = 36. So, what you have is 15/36 + 28/36 Now all the "units" are the same. Just as you ...
July 13, 2014

maths - oops
Err, I mean one leg=2. So half the chord has length √21
July 13, 2014

maths
Draw a diagram, including the radii to the ends of the chord. Draw the radius perpendicular to the chord. You now have two right triangles with one leg=1 and hypotenuse=5. Half the length of the chord is √24.
July 13, 2014

Algebra II
no, since 2x^2+x-15 = (2x-5)(x+3) Just multiply both sides by (2x-5)(x+3) The thing to watch out for is to be sure to note that 5/2 and -3 must be excluded from the domain.
July 13, 2014

mat/117
you want where P < 0 P(x) = 750x(20-x) You know that P=0 when x=0 or 20 Since the graph is a parabola opening downward, P>0 between the roots. So, P<0 if x>20
July 13, 2014

mat/117
translating upward just means add 11 to g.
July 13, 2014

mat/117
f(x) = -5(x - 3/10) + 29/20 If that doesn't tell you the answer, review your forms of quadratics.
July 13, 2014

mat/117
(fg)(x) = f(x)*g(x) = (-6x-1)(4x^2)
July 13, 2014

mat/117
(f+g)(x) = f(x) + g(x) so, just add the two polynomials together.
July 13, 2014

phi 208
life is like a simile.
July 13, 2014

Math
ok. now what?
July 13, 2014

math
Surely this treated in your text. You want A/(v-1) + B/(v+2) = 1/(v-1)(v+2) A(v+2) + B(v-1) = 1 Av + 2A + Bv - B = 1 (A+B)v + (2A-B) = 0v + 1 For those polynomials to be identical, all of the coefficients must match. So, we have A+B = 0 2A-B = 1 solve those and you get A = 1/3...
July 12, 2014

math
You use partial fractions. 1/(v+2)(v-1) = 1/3 (1/(v-1) - 1/(v+2))
July 12, 2014

science
light is reflected from both sides of the glass.
July 12, 2014

algebra
set x=0 and evaluate y. That's the y-intercept. Ax+By=C has slope -A/B because By = -Ax+C y = -A/B x + c/B In this case, A=9 and B=5
July 12, 2014

math
look at your functions. They indicate that the ball rises as time goes on, and never comes back down. h1(t) = 156 - 16t^2
July 12, 2014

MATH
IF UNIT IS 1, HOW ABOUT 9871 ?
July 12, 2014

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