Thursday

July 28, 2016
Total # Posts: 42,137

**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*

**programming**

looks ok to me
*June 27, 2016*

**Math**

That's a salary bump twice a year, so 6000 + 50(2*5)
*June 27, 2016*

**Urgent help here! Math**

can't see the shaded area, but clearly the circle has radius 5.
*June 27, 2016*

**physics**

or, -1.5 km/hr/s
*June 27, 2016*

**value**

puqloDwI' ja'pu'vawq Dayep pe'vIl chop Ho'Du'Daj; pe'vIl Suq pachDu'Daj Ha'DIbaH puv juchyub yIyep bInDepSuHach vaQeHmuS ghombe' DanIDjaj
*June 27, 2016*

**Maths**

3a:2c
*June 27, 2016*

**mathenatic**

garbled English, but I think you want 6/2 (2a+5d) = 72 a+d = 7(a+64d) solve that for a and d, and then evaluate 10/2 (2a+9d)
*June 27, 2016*

**Math**

just go to any online unit conversion site. There are many good ones, such as http://www.onlineconversion.com/
*June 26, 2016*

**Please Help ..!Math**

1350/70/30 = 1710/x/28 x = 95
*June 26, 2016*

**math**

p * (1 - (11 + 1/9)/100) = 360 + 40
*June 26, 2016*

**science**

a = 2 + 1000/20
*June 26, 2016*

**math**

The question is mangled, but if you want to say that S17 = 359 S21 = 966 for an arithmetic sequence, then just solve 17/2 (2a+16d) = 359 21/2 (2a+20d) = 966 For a geometric sequence, you need a(r^17-1)/(r-1) = 359 a(r^21-1)/(r-1) = 966 In either case, the answers are not simple.
*June 26, 2016*