Sunday

December 4, 2016
Total # Posts: 46,800

**Calculus Reimann Sum**

so, how did you do it? If the interval is [-2,3] then each interval has length 1, so I fail to see how you got the fraction.

*November 4, 2016*

**algebra 1**

5x-2 passes through (8,38) So, you need to subtract 40 so it goes through (8,-2)

*November 4, 2016*

**Calculus**

Note the sum. You have a2-a1 + a3-a2 + a4-a3 + ... + a21-a20 = a21-a1 = 2^21 - 2^1 There's really no reason to write the sum as you did. Since you know a_i explicitly, it would be better just to say 20 ? 2^(i+1)-2^i i=1

*November 4, 2016*

**Calculus - Special sum formulas**

see your other post. Repeating it does no one any good. Don't forget your Algebra I now that you're taking Calculus!

*November 4, 2016*

**Calculus - Special sum formulas**

Huh? You have the answer. Just simplify if you want: n(n^2-37)/3

*November 4, 2016*

**Pre-algebra**

no. all whole numbers are rational (fractions with denominator=1, as in 2/1, 4/1, etc.) There are lots of numbers that are not rational (irrational), like ?, ?3, ?5, etc. They cannot be expressed as the ratio of two integers.

*November 4, 2016*

**Calculus**

a = 24t+4 v = 12t^2+4t+11 s = 4t^3+2t^2+11t+15 so, s(9) = ?

*November 4, 2016*

**Calculus - Differential Equations**

oh come on. 0+C = -4/6 C = -2/3 -4/u = t - 4/3 u = -4/(t - 4/3) = 12/(4-3t)

*November 4, 2016*

**Calculus - Falling Body Problem**

it is well known that the equations are s(t) = 3000+75t-16t^2 v(t) = 75-32t So plug and chug Extra credit: derive those equations.

*November 4, 2016*

**Calculus - Differential Equations**

so, crank it out: 4 du = u^2 dt 4/u^2 du = dt -4/u = t+C now plug in (0,6) to get C.

*November 4, 2016*

**Tricky Math Question**

However, if you look at the graph for y = x^x the limit near zero is 1. limit x^x log(limit) = x*logx = logx/(1/x) use l'Hospital's rule: = (1/x) / (-1/x^2) = -x log(limit)=0, so limit=1

*November 4, 2016*

**Pre-Algebra**

right Although we're not really using the associative property. That would state that (2.25 • 23) • 4 = 2.25 • (23 • 4) All you did was evaluate the expression inside the parentheses and replace it with an equal value.

*November 4, 2016*

**Math**

well, the floor is 10x16 tiles in size, so ...

*November 4, 2016*

**ss**

well, surely you know that (a) N-S directions are latitude (b) N.A. is west of England...

*November 4, 2016*

**physics**

If ? is the angle upstream, then you have sin? = 2.5/7.3

*November 4, 2016*

**science**

y = tan? x - g/(2 (v cos?)^2) x^2 so plug in your numbers and solve for v when y(10) = 2

*November 4, 2016*

**MATHS**

which area? lateral, total, circular base? I'll assume the base. Volume = base_area * height

*November 4, 2016*

**Physics**

(v^2 sin2?)/g = v^2 sin^2?/g 2sin? cos? = sin^2? 2cos? = sin? tan? = 2

*November 4, 2016*

**Physics**

result of downward and sideways motion.

*November 4, 2016*

**Physics**

a = 7.2km/hr-s s = 1/2 * 7.2 * (10/3600)^2 + (72*20/3600 - 1/2 * 3.6 * (20/3600)^2) = .4km = 400m

*November 4, 2016*

**Math**

4 * 5 1/2 * 2 1/2 = 55 ft Extra credit: How many pieces is that? Are leftover portions after cutting to be used as needed?

*November 4, 2016*

**help help help sir steve**

Well! The method is similar to long division. If you have learned how to do square roots by hand, this method is just an extension of tat same algorithm. But to explain it here is not a good use of resources. If you google cube root by hand you will find many articles and ...

*November 4, 2016*

**math**

their areas are in the ratio (2/5)^2

*November 4, 2016*

**math**

the map figure has area a = (5+2)/2 * 4 = 14 cm^2 The area is 14 * 500^2 cm^2 Now just convert that to m^2

*November 4, 2016*

**maths**

Looks like 7 to me, since it is the only number unused in the other phrases, which also mention bring and apple.

*November 4, 2016*

**Math**

585 = 0.9 x

*November 4, 2016*

**Science**

how many moles? M = moles*(1000/100)

*November 4, 2016*

**Math**

see the related questions below, and use your numbers.

*November 4, 2016*

**mathe arithmetic progression**

sorry - fix your typo, then we can get somewhere.

*November 4, 2016*

**communications**

communications

*November 4, 2016*

**Algebra 2**

f(x) = 4 for 0 <= x < 3 f(x) = 6 for 3 <= x < 6 ...

*November 4, 2016*

**Math**

90 * 30/5

*November 3, 2016*

**Math**

((10-3)+(8-3))*x = 60

*November 3, 2016*

**Physics**

surrounding air is humid

*November 3, 2016*

**Calculus**

so, you seem to have the diagram down. Now just define the cost function and minimize it. What do you get? Is your 30-60-90 triangle you final answer, or some intermediate stage?

*November 3, 2016*

**Finite math**

there are 2^3 = 8 subsets of S. see where that takes you.

*November 3, 2016*

**calculus**

see related questions below.

*November 3, 2016*

**Math**

If he had x lbs of flour, 2/5 x = 16 x = 40 so now you can answer the question...

*November 3, 2016*

**Math**

well, 15-2 = 13 see what you can do with that.

*November 3, 2016*

**Math**

looks like each topping costs $1.50 so ...

*November 3, 2016*

**precalculos**

for each part, just divide the total cost by how many calculators: C(x)/x

*November 3, 2016*

**Adv function**

sin(7x) = sin(x+6x) = sinx cos6x + cosx sin6x = sinx*cos(2*3x) + cosx*sin(2*3x) ...

*November 3, 2016*

**Math**

assuming no friction, consider the cases of 0°: 0 force 90°: full weight Looks like weight * sin(angle)

*November 3, 2016*

**Math-PreCalc**

Draw a diagram. The resultant is just the hypotenuse of the triangle with u and v as legs. The angle t with u is tan(t) = 30/47

*November 3, 2016*

**Calc**

see related questions below

*November 3, 2016*

**Calculus - YES! @Reiny**

*whew* what a relief that we agreed!!

*November 3, 2016*

**Calculus**

what, no effort since you last [posted this problem? Most of it is just geometry. If the radius is r and the cylinder length is h, then 4/3 ? r^3 + ?r^2 h = 1600 so h = (4800 - 4?r^3)/(3?r^2) = 1600/?r^2 - 4r/3 If the sides cost $1/ft^2, then the ends cost $2/ft^2, so the cost...

*November 3, 2016*

**Math**

total:red = 14:3 12/20 = 3/5 = red:yellow 8 hours is 4 times as long as 2 hours, so it will go 4 times as far. Your answer is the distance gone in 2/4 hours. It should have been immediately clear that your number was too small, since the plane had more time. Keep your ratios ...

*November 3, 2016*

**Math**

Just do what you always do to isolate one variable. c/xy = (3d/4-ab) c/xy = (3d-4ab)/4 4c/(3d-4ab) = xy x = 4c / y(3d-ab)

*November 3, 2016*

**Math**

clearly, since there are asymptotes there, g' is undefined. It might be increasing or decreasing near the asymptote, but g'(-2) and g'(4) are undefined.

*November 3, 2016*

**Math**

correct. It has to be continuous to be differentiable.

*November 3, 2016*

**Algebra**

yes.

*November 3, 2016*

**Calculus**

Great. No matter which way you do it, you have to divide the region into two parts because of the boundary changes. So, the area could be either ?[0,1] (x - x/8) dx + ?[1,2] (1/x^2 - x/8) dx = 3/4 ?[0,1/4] (8y - y) dy + ?[1/4,1] (1/?y - y) dy = 3/4

*November 3, 2016*

**math**

(380/268) * 4.5 hours

*November 3, 2016*

**maths help**

well, just write the terms and equate powers: (p+x)^n = p^n + np^(n-1) x + n(n-1)/2 p^(n-2) x^2 + ... so, p^n = 3q np^n/p = 6q n(n-1)/2 p^n/p^2 = 5q n*3q/p = 6q 3n=6p n=2p n(n-1)/2*3q/p^2 = 5q 3n(n-1)=10p^2 3(2p)(2p-1)=10p^2 12p^2-6p=10p^2 2p(p-3)=0 p=0 or 1, but not 0, so p=3...

*November 3, 2016*

**math**

all those (unbalanced) parentheses! I suspect a typo. I'll try lim(n??)??(n^2+n)-n = n(?(1+1/n) - 1) = (?(1+1/n)-1)/(1/n) Let u = 1/n and you have (?(1+u)-1)/u = (?(1+u)-1)(?(1+u)+1) / (u?(1+u)+1) = (1+u-1)/(u?(1+u)+1) = u/(u(?(1+u)+1)) = 1/(?(1+u)+1) lim as n?? = lim as u...

*November 3, 2016*

**algebra**

-5x^4 + x - 4/x

*November 3, 2016*

**Math**

hey are just sides of a (possible degenerate) triangle, so 5-4 <= |u+v| <= 5+4

*November 3, 2016*

**Maths**

total distance: 12 km total time: 6/4 + 6/12 = 2 hr so, ...

*November 3, 2016*

**math**

f = e^(x^2-2x) f' = (2x-2) e^(x^2-2x) since e^(x^2-2x) is always positive, f'=0 at x=1 f" = (4x^2-8x+6)e^(x^2-2x) f"(1) > 0 so f(1)=1/e is a local minimum. Now just check f(0) and f(2) to find the absolute extrema for the interval.

*November 3, 2016*

**maths**

(a) Find the points which divide the line joining A(1,3) and B(-4,-1) internally in the ratios: (ii) 1:1 (iii) 3:1 (b) On the same x-y axes plot the point A(1,3) and B(-4,-1) and draw the line joining them. Add the three points which you calculated in part (a).

*November 3, 2016*

**math**

sinA = 1/2 cosA = ?3/2 tanA = 1/?3 plug those in and see where it takes you

*November 3, 2016*

**Math**

1/2 in:4 ft = 5/2 in:20 ft

*November 3, 2016*

**calculus**

v^2 = rg tan(?) 2v dv/dt = rg sec^2(?) d?/dt

*November 3, 2016*

**calculus**

If x is the distance from the closest point on the wall, x/50 = tan? 1/50 dx/dt = sec^2(?) d?/dt

*November 3, 2016*

**calc**

If the light is at height h, we know that 6/12 = h/18 h = 9 So, if the shadow has length s when the man is x feet from the pole, then we have s/6 = (x+s)/9 s = 2x so, ds/dt = 2 dx/dt Now just plug in your numbers.

*November 3, 2016*

**calclus**

draw a diagram. If x feet of line are out, 15/x = sin? -15/x^2 dx/dt = cos? d?/dt Now just plug in your numbers.

*November 2, 2016*

**Calculus**

By inspection, f(10)=40, so f^-1(40) = 10 finding f^-1(x) is quite hard, since you have to solve a cubic. http://www.wolframalpha.com/input/?i=inverse+2x%E2%88%9A(x-6)

*November 2, 2016*

**Calclus**

well, dy/dt = -2x/(1+x^2)^2 dx/dt so plug in x = -2

*November 2, 2016*

**Algebra**

there are many: (1,4) (10,0) (-5,22) and lots lots more

*November 2, 2016*

**time speed and distance**

Break the total time into three periods: x: when a&b are on the bike y: when a rides back for c z: when a&c are on the bike since distance = time*speed, write the net distances traveled by each person: a: 50x-50y+50z = 40 b: 50x+10y+10z = 40 c: 10x+10y+50z = 40 Now solve for x...

*November 2, 2016*

**math**

v = 3495 - (3495/5)t

*November 2, 2016*

**Calculus**

v = 4/3 pi r^3 dv/dt = 4 pi r^2 dr/dt Now just plug in your numbers.

*November 2, 2016*

**Math**

break them into x- and y-components, then add. Then convert back to polar form. F1+F2 = <5/2,5?3/2>+<0,8> = ?

*November 2, 2016*

**Math**

1/7 * 9/8 = 9/56

*November 2, 2016*

**Math**

huh. I saw the ? and thought of vector differentiation. But the set of elements and the v5 throw me. Care to explain what this is all about?

*November 2, 2016*

**Adv function**

divide top and bottom by cos^2 (multiply by sec^2) and you have sec^2(x)/(1-tan^2(x))

*November 2, 2016*

**Math**

((?2 x) + k)^2 = 2x^2 + 2?2 kx + k^2 So, we need k=±5 That means a = ±10?2

*November 2, 2016*

**Math**

what is 8^2 + 2^2 ?

*November 2, 2016*

**Maths**

I will assume that you plugged in 5 for x to justify your answer.

*November 2, 2016*

**math**

If it takes x quarts to paint the inside, then you have x + x+19 = 107 Now adjust that so it answers the question.

*November 2, 2016*

**Plane Trigonometry**

Draw your triangles. You will then see that sinA = -4/5 cosA = 3/5 sinB = -3/7 cosB = -?40/7 Now just plug those into the formula for cos(A-B)

*November 2, 2016*

**Math**

If they lost x games, then x + x+17 + 3 = 52

*November 2, 2016*

**Math, Precalc**

It's annoying how you don't want to show your work. Just let us take care of it all. Just for readability, try letting u = 1/x. Then you have 6*(9^u)-13*(6^u)+6*(4^u))=0 6*3^(2u) - 13*3^u*2^u + 6*2^(2u) Now if you let v=3^u and z=2^u you have 6v^2 - 13vz + 6z^2 = 0 (3v...

*November 2, 2016*

**Math, Precalc**

You have powers of 2 and 3. Expand all the groups, collect the powers, and solve for x. If you get stuck, show what you got done.

*November 2, 2016*

**Plane Trigonometry**

draw your triangles in standard position. It will be clear that sinA = 4/?41 cosA = -5/?41 sinB = -12/13 cosB = -5/13 Now just plug that into the formula for cos(A+B) Although I suspect a typo...

*November 2, 2016*

**geography**

if you google those choices including the word "Iran", it should be clear.

*November 2, 2016*

**geometry**

geez. Just look at the diagram. It should be clear what part of the triangle is used. No idea at all? And sorry, can't do constructions here. I'm sure google can help out though.

*November 2, 2016*

**algebra 2**

and ... ? Don't make us figure out the question, as well as the answer!

*November 2, 2016*

**PLZ CHECK ANSWERS**

#11. Nope. Your answer is -3 7/9 + 1 2/9 #12. Nope. 6 1/3 - 4 4/9 = 6 3/9 - 4 4/9 = 5 12/9 - 4 4/9 = ...

*November 2, 2016*

**Math**

Actually, Lebanon had the smallest population! And it is customary to write 10^6 for a power, since yours looks like just the number 106.

*November 2, 2016*

**plz plz help me belive me have tried**

I am Leo I Just changed my name to Steve because I thought I'd get in trouble

*November 2, 2016*

**plz plz help me belive me have tried**

Let A = (X+Y)/2 and B = (X-Y)/2. a = sin X + sin Y = sin(A+B) + sin(A-B) = 2 sin A cos B b = cos X + cos Y = cos(A+B) + cos(A-B) = 2 cos A cos B a/b = (2 sin A cos B) / (2 cos A cos B) = tan A sin A = a/?(a² + b²) cos A = b/?(a² + b²) sin(X+Y) = sin 2A = 2...

*November 2, 2016*

**Oops^2**

Holy smoke! I just noticed another typo. The correct solution is: 3/(1 1/4) = 3/(5/4) = 3 * 4/5 = 12/5 = 2 2/5 But I'm sure you already figured it out ...

*November 2, 2016*

**Oops**

I see that my answer is not one of the choices. Can you see my typo? 16/5 = 3 1/5, not 5 1/3 Never think you're done just because you arrived at answer. Always check it!

*November 2, 2016*

**MATH STEVE**

suppose I asked you how many pieces of 3 ft each you could cut from a 15-foot string. How would you do it? Divide the total length by the length of each piece, right? Same here. Don't be flummoxed by the fractions -- they're just numbers like any others. 3/(1 1/4) = 3...

*November 2, 2016*

**maths**

The net for a unit cube has a perimeter of 14. So, yours has a perimeter of 70

*November 2, 2016*

**Math (Help!)**

I don't know what to do either, since all you dis was post an expression with no question. If you want to see what it simplifies to, do multiplication first, then addition: 5x2+6-5 = 10+6-5 = 16-5 = 11 If you really have no clue, you seriously need to review the material ...

*November 2, 2016*

**Math**

0 < 1/9 < 1/4, so it rounds to 0 1/2 < 14/27 < 3/4, so it rounds to 1/2

*November 2, 2016*