Thursday
December 8, 2016

Posts by Steve

Total # Posts: 46,999

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
42
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

Calculus
f' = 4x^2 f = 4/3 x^3 + C Since f(-1)=3, (4/3)(-1)+C = 3 C = 13/3 So, f(x) = 4/3 x^3 + 13/3 do the other one in like wise.
November 2, 2016

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