Sunday
July 24, 2016

Posts by STEVE

Total # Posts: 42,049

Math
the radius is r = 44/2π = 22/π so, now do the area, πr^2
July 1, 2016

Precalculus
I assume you know how to write sigma: ∑ Note that the numerators go from 3 to 8, alternating signs, and the denominators count down from 8 to 3: 8 ∑ (-1)^k * k/(11-k) k=3
July 1, 2016

Precalculus
n years after 2016, the price will be 12.00 * 1.05^n 12*1.05^14 12*(1.05^14 - 1)/(1.05 - 1) check out your geometric series stuff
July 1, 2016

Math
Now you see why parentheses are important: (x+2)/(4-x) + 1/3 > 1/2 (x+2)/(4-x) > 1/6 If x<4, 6(x+2) > 4-x 6x+12 > 4-x 7x > -8 x > -8/7 So, one solution is the interval (-8/7,4) If x>4, 6(x+2) < 4-x x < -8/7 Not possible, sine we started out with x...
July 1, 2016

physics
245cm^3 ------------ = 21.7s 11.3cm^3/s
July 1, 2016

Chemistry
C2 yields 2CO2 H6 yields 3H2O but that leaves us with 7O, and O only comes in O2 molecules. So, double everything to get 2C2H6 + 7O2 = 4CO2 + 6H2O on the left: 4C 12H 14O on the right: 4C 12H 14O it balances
July 1, 2016

Gupta
x+y = 45 1/x + 1/y = 1/10 the two resistors are 15 and 30 ohms
July 1, 2016

Chemistry
2Bi + (3/2)O2 = Bi2O3 But we don't have 1/2-molecules, so double everything to get 4Bi + 3O2 = 2Bi2O3
July 1, 2016

math
(75*40 - 2.5*1.5)*6 = ?
July 1, 2016

math
7*10^3 * 2*10^4 = (7*2)*10^(3+4) = 14*10^7 = 1.4*10^8
July 1, 2016

Stoichiometry
How many moles of H2SO4 in 10g How many moles of H2O for each mole of H2SO4? How many grams per mole of H2O?
July 1, 2016

math
19+6√2 what about it?
July 1, 2016

maths
43-12√7 no calculator? just type it in at google.com or you can do more complicated stuff at wolframalpha.com Hard to believe that someone who knows how to use a computer needs help with this kind of problem.
July 1, 2016

value
recall that (a+b)(a-b) = a^2-b^2 then multiply top and bottom by 2√5-3√3 and you have (3√5-√3)(2√5-3√3) -------------------- (2√5+3√3)(2√5-3√3) 6*5 - 2√15 - 9√15 + 3*3 ----------------------------  &...
July 1, 2016

Math
20-8 = 12
July 1, 2016

Math
If the original fraction is n/d, then we are told: 4n/(d-2) = 2 (n+15)/(2d-2) = 9/7 n/d = 3/8
July 1, 2016

Math
x+y = 24 x-6 = 3(y-6) Now just find x and y
July 1, 2016

physics
h/80 = tan 12°5'
July 1, 2016

Math
it will be a square, using 196 tiles (14x14)
July 1, 2016

MATH
(a) .20*900 + .30*300 (b) divide that by 1200
July 1, 2016

math
mode is the most common entry: 25
July 1, 2016

math
y = 1x+135 y = 2x+12 y = 3x-111 or many other possibilities. A single point does not give much information.
July 1, 2016

Math
y = 25+25*[[x]] where [[x]] is the greatest integer less than x.
June 30, 2016

geometry
Can't tell whether A is in between B and E or not. But, you know that BEC=BED That should help you pin down AEC. If A is between B and C BEA+AEC=BEC 11x-12 + AEC = 4x+1 AEC = 13-7x or, if B is between A and C, AEC-AEB=BEC AEC-11x+12 = 4x+1 AEC = 15x-13 Of course, A could ...
June 30, 2016

solid geometry
oh, right. I forgot about the circle. Hmmm. Still seems a bit murky. I see that if the radius of the circle is r, r^2+8^2 = MB^2 MB^2+MA^2 = AB^2 so, AB^2 = r^2+64+28 = r^2+92 But I can't figure out how to pin down r. Maybe you can take it from here.
June 30, 2016

solid geometry
BC is a tangent to what? I see line MA sticking up out of the plane X and B in the plane, but where is C?
June 30, 2016

Calculus
Hmmm. So the curve is tangent to the x-axis at (-1,0) and (1,0) and has a point of inflection at (0,0)? I don't see how that can be. The critical points work, but they cannot also be points on the curve. It calls for too many changes in direction. I suspect the problem has...
June 30, 2016

Calculus
Sure looks like a typo to me. Given that f'=0 at x = -1 and x=1, f'(x) = k(x-1)(x+1) = x^2-1 That would make this just a plain old cubic curve, concave down for x<0 and concave up for x>0. Then things fall into place and I think a good graph would be y = x^3-3x ...
June 30, 2016

Calculus
both (-1,2) and (-1,0) are on the graph? Is x a function of y?
June 30, 2016

math
What do you want to do? find a and b? f(x) = (x-1)(x-4)(x^2+ax+b) g(x) = (x-3)(x+2)(x^2+3x+b) we know that (x-3) divides x^2+ax+b (x-1) divides x^2+3x+b so, b+4 = 0 and b = -4 3a+5 = 0, so a = -5/3 f(x) = (x-1)(x-4)(3x+5)(x-3) g(x) = (x-3)(x+2)(x-4)(x+1)
June 30, 2016

geometry
well, you know that the circle with center at (h,k) and radius r is (x-h)^2 + (y-k)^2 = r^2 so what do you think?
June 30, 2016

Math
in base 4, since 8x8=64 = 4^3, that would be 10 x 10 x 1000 = 100000
June 30, 2016

science
since dv/dt = -2v v(t) will be an exponential function, so it will never be zero. You sure you don't want to specify some small acceptable speed at touchdown? Anyway, consider that after falling for k seconds, v = -9.8k and after t more seconds when s=0, you want v close ...
June 30, 2016

History
both what? Want to try that sentence again?
June 29, 2016

Stat
each ticket has an expectation of (900+2*700+2*400+5*200)/1000 = $4.10
June 29, 2016

Calculus
a box with base of side x has height 150/x^2 So, the cost function is c(x) = 10*2*x^2 + 20*4*x*150/x^2 = 20x^2 + 12000/x so, find where dc/dx=0 for minimal cost.
June 29, 2016

Calculus
If there is no limit to the dimensions of the page, a square will have minimal area. If the printed area is 12x12, the sheet is 15x15 with area 225 6x24, the sheet is 9x27 with area 243 1x144, the sheet is 4x147 with area 588. I think you have left out some pertinent ...
June 29, 2016

Math(Please Help Assignment Due Now
that's 1σ below the mean.
June 29, 2016

solid geometry - incomplete
No idea where B and C are. But you will certainly be using the Pythagorean Theorem on the resulting line segments.
June 29, 2016

Math
well, just plug in x = -2 and set the result to 4: x√(x+k) + 6 = y (-2)√(-2+k) + 6 = 4 -2√(k-2) = -2 √(k-2) = 1 k=3 If you meant that second * operator, then fix the expression and follow the steps again.
June 29, 2016

Math- Assignment Due
#1 See the excellent step-by-step article at https://mathway.com/examples/Statistics/Frequency-Distribution/Finding-the-Standard-Deviation?id=1040 Use your data values where they used interval-midpoint values (M). For the others, use the handy tool found at http://davidmlane....
June 29, 2016

Algebra
B=10 So, A=84 So, C=900
June 29, 2016

calc
ok ok ok I did one. Can you follow my logic and try the others? They're all done the same way. Decide the limits of integration, and then use discs: v = ∫πr^2 dx shells: v = ∫2πrh dx or dy, depending on how you want to integrate. Just decide on r and ...
June 29, 2016

CALC
PS Did you see my typo, and that it makes no difference in the answer?
June 29, 2016

CALC
The 19/3 is just a nuisance constant. Don't know why they stuffed it in there. I'll just do the integral with a constant k, and it will make things easier to read. y = kx(x-1) crosses th x-axis at x=0 and 1. So, using discs of area πr^2 and thickness dx, the ...
June 29, 2016

math
come on. what are 1+7 and 9-4 ?
June 29, 2016

Math easy HELP
you need all the powers to be 3, so 360 * 3*5^2 = 2^3 3^3 5^3
June 29, 2016

math
The 3 digits must be 2,4,6 in any order.
June 29, 2016

Analytic Geometry
the diameter of the circle is the hypotenuse of the right triangle. The diagonal of an isosceles right triangle of side a is 2√a
June 29, 2016

trig
105 = 60+45 tan 105° = (√3+1)/(1-√3)
June 29, 2016

Math
22.00 * 0.08 22.00 * 0.08 * 12
June 29, 2016

math
326 mi/hr is the speed of a car going 5.433 times as fast
June 29, 2016

Algebra
in the first 2 hours, A moved 80 miles. B is going 14 mi/hr faster than A. So, it takes 80/14 hours to catch up.
June 29, 2016

Physics
a = ∆v/∆t = (10/1.5) km/hr/s 36-30 = (30-20) * 6/10 so, it will take 6/10 as long to make that change
June 28, 2016

mathematics-Rate
5 women can do the work of 4 men in an hour. So, the combined crew is the same as having 12 men. That means that one man can cut 1/60 of the field in an hour. Now you can see how many men it will take to do the job in 3 hours.
June 28, 2016

calculas
Still no good, but let's assume you have 3xy-6x+2y^2 = 0 Then 3y dx/dt + 3x dy/dt - 6 dx/dt + 4y dy/dt = 0 (3x+4y) dy/dt = (6-3y) dx/dt dy/dt = 3(2-y)(dx/dt)/(3x+4y) dy/dt = 3(5)(-6)/(6-12) = 15 But that's so only if my original equation is close.
June 28, 2016

calculUs bogUs
Neither do I. You haven't asked a question. If you want dy/dt at (2,-3) then you just need to do 3y + 3x dy/dt - 6 + 4y dy/dt but you can't evaluate anything, because you have no equation. Why not try posting the entire question, not just part of it?
June 28, 2016

Geometry
no diagram, no TeX
June 28, 2016

math
20000 - 10001 = 9999
June 28, 2016

Chemistry
how many moles of NaOH in 1.06 g? half that many moles of H2SO$, since H2SO4 + 2NaOH = Na2SO4 + 2H2O
June 28, 2016

chemistry
well, the final solution total mass must be 5.00/.162
June 28, 2016

geometry
the first step is not to post the same problem twice, one minute apart!
June 28, 2016

math
Draw a diagram. There is a right angle at the horizon, so the distance d is 4000^2 + d^2 = (4000 + 29035/5280)^2 you can compare that to the estimate of d = √(2Rh)
June 28, 2016

math
sinx = 1/2 cosx = -√3/2 siny = -1/√2 cosy = 1/√2 Now just plug in your values: (-1/√3 - 1)/(-√3/2 - 1/√2) = I'll let you massage that to a more pleasant appearance.
June 28, 2016

geo
Maybe VU/2 ?
June 28, 2016

maths
In case you have mislaid your formulas, you can get them from the excellent article at wikipedia: https://en.wikipedia.org/wiki/Trajectory
June 28, 2016

Math roster form
Yo do know what integers are, right? {-2,-1,0,1,2}
June 28, 2016

algebra
If x is invested at 2%, then .02x + .04(49500-x) = 1770
June 28, 2016

math
x(100-2x) or x(100-x)/2 depending on which side is chosen to be x. This assumes, of course, that (a) the river bank is straight (b) the area uses the bank as one side
June 28, 2016

math
well, the only digit not given explicitly, is the tens. So, what is 1 more than 4?
June 28, 2016

math
I have no idea what the yield is, but I can get the area. Mark off the rectangle with the short base as one side. That leaves two right triangles, each with height h, and bases x and 15-x. So, x^2 + h^2 = 14^2 (15-x)^2 + h^2 = 13^2 Solving that, we get h = 56/5 So, the area of...
June 28, 2016

math
x-2 = 5 x = 7 3x = 21
June 28, 2016

Math
copy/paste font problems, but 55-35 = 20° = π/9
June 28, 2016

Maths - eh?
you cannot mean that the number of benches equals the number of rows, since 1450 is not a perfect square. So, you must mean that each row had the same number of benches. So, what are the factors of 1450? I suspect a typo or a garbled question.
June 28, 2016

math
x miles is 4x quarter-miles, so c + s(4x-1)
June 28, 2016

math
3(x-2 + x) = 30
June 28, 2016

Calculus
Or, rearranging things a bit, -y(2x^2y+1) / x(x^2y-2y^2+1) = -y(2x^2y+1) / x(x^2y-y^2-1 + 2-y^2) = y(2x^2y+1) / x(2-y^2+ln(xy))
June 28, 2016

math
just plug in your basic equation of motion: s = vt + 1/2 at^2 Now just use your numbers for v and a and t.
June 27, 2016

maths
If one angle is x, then the other is x+18. So, x + (x+18) = 90
June 27, 2016

math
Looks like you found the easy way -- get someone else to do the work. p = 2.2 q p = r + 350000 q = r + .05(p+q+r) Now just find p,q,r and add them up.
June 27, 2016

Math3( Please Help Assignment Due)
you can enter your data at http://davidmlane.com/hyperstat/z_table.html
June 27, 2016

HISTory
why do you think? It was painted by a great master, during the Renaissance. It's a famous painting of that period, typical of the style then.
June 27, 2016

rio hondo
minimum at x = -1/14
June 27, 2016

Calculus - Discontinuity
It is only removable if f(x) is defined to be the same as the limit value. If f(x) were 7 at x=3, then that would plug the hole. But since it is defined to be a different value, it creates a jump which cannot be joined to fill the hole.
June 27, 2016

Calculus - Discontinuity
jump. f(x) = 2x+1 everywhere except x=3. Since the limit from both sides is 7, but f(3)=6, there's no way to remove that break.
June 27, 2016

Math2(Please Help Assignment Due)
I think you mean two congruent sides. The angles are Q=86 R=86 P=8 You know that q=r=44, so you just have to find p. Using the law of sines, p/sin8 = 44/sin86
June 27, 2016

Math( Please Help, Assignment Due)
Draw a diagram. Using the law of sines, the distance x you want is x/sin40 = 550/sin80
June 27, 2016

Calculus
everywhere except x=3, F(x) = 2x+1 Since 6≠7 you have a jump there. The limit from both sides is 7, but F is defined to be 6, and there's no way to close that gap.
June 27, 2016

calculus
6t dy/dt + y = √t y' + 1/6t y = 1/(6√t) You want an integrating factor: e^(∫1/(6t) dt) = t^(1/6) Now the equation becomes t^(1/6) y' + 1/6 t^(-5/6) y = 1/(6∛t) d(t^(1/6) y) = 1/(6∛t) t^(1/6) y = 1/4 t^(2/3) + c y = 1/4 √t + c/t^(1/6)
June 27, 2016

calculus
We have dA/dt = 2*4 - 1/(200+3t) A(0) = 100 and we want to find A(100) So, just solve the differential equation, and then plug in t=100, since at a net gain of 3 gal/min, the tank will be full at t=100.
June 27, 2016

Maths - eh?
Hmmm. Is it not 7P4 = 7!/3! ?
June 27, 2016

calculus
for any point on the curve, the distance z to (2,0) is z^2 = (x-2)^2 + (y-0)^2 = x^2-4x+4 + x+3 = x^2-3x+7 so, use z = √(x^2-3x+7)
June 27, 2016

Calculus - typo?
you dropped something out
June 27, 2016

Maths
√1700 = 41.23 So, any factor of 1700 less than that could be the length. So, you could have any integer dimensions from anything in this list: 1x1700 2x850 ... 25x68 34x50
June 27, 2016

math - woefully incomplete
an argument could be made for almost any number. One data point does not give much to go on.
June 27, 2016

math
120 is already rounded I think you left something out
June 27, 2016

Dahal
a wild-eyed political dissident
June 27, 2016

Dahal
every second v decreases by 1/2 m/s so, it takes 40 seconds to stop The distance covered during time t is s = 20t - 1/4 t^2 Now just plug in t=40
June 27, 2016

calculus
If they are changing at opposite rates, the slope is -1 dy/dx = 2x so when is that -1?
June 27, 2016

Algebra
x-y = 96 x+y = 300 solve that, or reason thusly: 150+150=300 difference is zero The difference is 96, so subtract 48 from one number and add 48 to the other: 102+198 = 300 difference is 96
June 27, 2016

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