Thursday
November 27, 2014

Posts by steve


Total # Posts: 27,026

Math
well, r = -3/6 = (3/2)/-3 = (-3/4)/(3/2) ... 6/2 = ? (-1/2)/1 = ?
October 8, 2014

Math
have you a calculator? Just do the math...
October 8, 2014

Sociology (Stats) Std. Dev
600 is 1 std above the mean. 300 is 3 std below the mean. Just look up the tails in your table. Or, play around some at http://davidmlane.com/hyperstat/z_table.html
October 8, 2014

help
h(t) = 5 + 70t - 16t^2
October 8, 2014

math
5% up, or 5% down? In any case, what's 5% of 85000?
October 8, 2014

math
It's roughly 55000/50 = 1100 the estimate will be low, because we lowered the divided and raised the divisor.
October 7, 2014

Math
#1 clearly, r = -1/2 T11 = ar^10 #2 a(-2)^9 = -1024 #3 Just recall that S = a/(1-r) then plug in the numbers
October 7, 2014

pre-calculus
well, 9 is half of 18, so ...
October 7, 2014

Math
#1 think 8^n #2 .123 123 123 = 123/999 same for the others
October 7, 2014

calculus
The math looks good to me, but the negative answer is strange because the question was, how fast is the angle increasing? That is because dx/dt = -600; the plane is approaching the kangaroo. Hailey, did you do as Reiny asked, and check his math?
October 7, 2014

math
20 kg * 2.2 lb/kg * 50 mg/lb * 1mL/100mg = 22 mL
October 7, 2014

Math
well, what's the mean? 86.2 The deviations from the mean are thus 8.2, 4.2, ... Now just take the mean of those values. That's the mean deviation.
October 7, 2014

Pre-Calc/Trig..
I think I prefer y = 2(x-3)^2
October 7, 2014

Calculus question
simple, but tedious. See http://en.wikibooks.org/wiki/Trigonometry/Simplifying_a_sin%28x%29_%2B_b_cos%28x%29
October 7, 2014

math/physics
conserve momentum: 0.600(+4.00) + 1.00(-5.00) = 1.00(-7.25) + 0.600v v = +7.75 Now, what's wrong with this picture?
October 7, 2014

Calculus
of course -- where y=0
October 7, 2014

Algebra
I get 2.9 how did you get your answer?
October 7, 2014

math
if the angle is x, 12/22 = tan(x)
October 7, 2014

Math
apparently the formula is d = v√(h/4.9) multiply that by √4.9/√4.9 and you have d = v√(4.9h)/4.9 Now just plug in the numbers.
October 7, 2014

physics
PE at top: mgh = 35.9*9.8*20.3 = 7142 J She loses half that on the way down. KE = 1/2 mv^2 = 3571 So, v^2 = 3571/35.9 = 99.47 Call it 100 So, v = 10
October 7, 2014

calculus
√(2x+4y) + √(2xy) = 13.4 (x+2y) / 2√(2x+4y) * (2+4y') + 1/(2√xy) * (2y + 2xy') = 0 (x+2y)/√(2x+4y) + 2(x+2y)y'/√(2x+4y) + √(y/x) + √(x/y) y' = 0 y' = -[(x+2y)/√(2x+4y)+√(y/x)]/[2/√(2x+4y...
October 7, 2014

Calculus
The distance traveled after t hours is: If boat N is at (0,y) boat E is at (x,0), then the distance z from N to E is z^2 = x^2+y^2 At the given moment, z=√(56^2+20^2) = √3536 = 4√221 2z dz/dt = 2x dx/dt + 2y dy/dt Now plug in the numbers (after canceling out ...
October 7, 2014

math
I'd say 2x where x is the cost of one book
October 7, 2014

AP Calculus
f(x+h) = 1/√(x+h) + x+h f(x) = 1/√x + x f(x+h)-f(x) = 1/√(x+h) - 1/√x + h = (x+h)^(-1/2) - x^(-1/2) + h From the binomial theorem, (a+b)^n = a^n + n a^n-1 b + ... (x+h)^(-1/2) = x^(-1/2) - 1/2 x^(-3/2)h + 3/8 x^(-5/2)h^2 + ... where ... is stuff with ...
October 7, 2014

Algebra
Woah! Where did the 15# bags come from? Clearly, there will be more bags if the hold less.
October 7, 2014

math
ever heard of a calculator? Why would you post such a trivial problem? It takes much less time just to punch it in on your calculator, and you don't have to wait for and endure snide replies. Do you not trust your calculator? Is there something else about multiplication ...
October 7, 2014

Math
assuming you want trim all around, and plan to use miter cuts at the corners, then you need 2(10 3/4 + 129/10 3/4) = 45 1/2 ft see how much was left unsaid?
October 7, 2014

Grammar
No ideas on any of them? Nominative case: I,he,she,we,they Objective case: me,him,her,us,them So, #3 she #6 them #7 our -- why? "our" is an adjective can you get the others?
October 7, 2014

math
if the area is 42 m^2, the side is √42 m So, the perimeter is 4√42 m. Now just do the math...
October 7, 2014

Physics
no calculus needed. Just plug in your formulas: h(x) = tanθ x - g/(2 (v cosθ)^2) x^2 = 0.75x - .0000547 x^2 That is just a parabola with vertex at (6855.6,2570.8) I expect you can find x when h=0.
October 6, 2014

math
clearly that would be 6*18 - 4*6 = ?
October 6, 2014

ap calc
lim (x->3) 4-(√(25-x2))/(3-x) Use l'Hospital's Rule to get = lim (x->3) (x/√(25-x^2)]/(-1) = (3/4)/(-1) = -3/4 Recall that dy/dx at any point on the circle is -x/y
October 6, 2014

Physics
yes. Friction is just another force; nothing special about it.
October 6, 2014

College Physics
a = (-284.4 m/s)/1.4s = -203.1 m/s^2 s = Vo t + 1/2 at^2 = 284.4*1.4 - 1/2 (203.1)(1.4^2) = 199.1 m
October 6, 2014

Math
If each member makes x candles, then 40x = 39(x+3) x = 117 So now you can find the total.
October 6, 2014

MATH
d/dx (x^5 + y^8) is indeed 5x^4 + 8y^7 y' Usually this is done in conjunction with implicit derivatives, where you have some equation like x^5 + y^8 = 7 and you wind up with y' = -5x^4/8y^7 which you then have to evaluate at some point. ------------------------------ h...
October 6, 2014

AP Calc
y^2 = x^2 + 4/x 2y y' = 2x - 4/x^2 y' = (2x^3-4)/x^2 * 1/2y = (x^3-2) / x^2y Now as long as y≠0, y'=0 when x=∛2 y(∛2) = ±√(∛4+4/∛2) = ±√(6/∛2) so that's ok. It looks like the only place with ...
October 6, 2014

algebra
Since F=k∆x, F/∆x is constant. So, if the unstretched length is Lo, 8/(76-Lo) = 14/(85-Lo) Lo = 64 cm
October 6, 2014

Pre Calculus
What part of your text's explanation don't you understand? Any explanation we can give here will say basically the same thing.
October 6, 2014

Math
plug in the values graph the function
October 6, 2014

Math
since y = 10/x, the slope of the tangent at (x,y) is -10/x^2 so the normal has slope x^2/10. So, we have a line with slope y/x = (10/x)/(x^2/10) = 100/x^3 so, where does 10/x = 100/x^3? x = √10 So, at (√10,√10), the slope is 1, and the normal line is just y = x
October 6, 2014

Math
Man, you're a better grouper than I am. The 18 made me think of 9*2, so I got x(x-3)^2 = x^3-6x^2+9x hmm. too many x^2, so 2(x-3)^2 = 2x^2-12x+18 aha - (x+2)(x-3)^2
October 6, 2014

Algebra
if a/b = q remainder r, then a = b*q + r Try it with some small numbers: 37/8 = 4R5 4*8+5 = 37
October 6, 2014

Algebra2
just solve the way you do an equation. Apply a step to all parts of the setup: -1 < 3+2x < 11 subtract 3: -4 < 2x < 8 divide by 2 -2 < x < 4 Ta-da! The other is even easier, since each is separate 1-x > -3 1+3 > x 4 > x 5x-1 > 19 5x > 20 x >...
October 6, 2014

Algebra II
We have a winner!
October 6, 2014

Algebra II
4(4x+1)^2 = 4(16x^2+8x+1) Better double-check your answer.
October 6, 2014

Pre Calculus
No, what it says is (x-c) is a factor of f(x). If (x-c) is a factor of f(x), then f(c) = 0 f(-2) = -4(-8)+5(4)+8 = 32+20+8 ≠ 0 So, (x+2) is not a factor of f(x). You can check this out at calc101.com by clicking on the "long division" button and entering your ...
October 6, 2014

Pre Calculus
I think you mis-stated the problem. Better go back and see just what the theorem says.
October 6, 2014

math geometry
As usual, draw a diagram. Half the chord is of length 4. Draw the radius through the chord's center. Now you have a right triangle with leg 4 and hypotenuse 8, which subtends an angle x such that sinx = 1/2 So, x = 30 degrees. The whole chord thus subtends an angle of 60 ...
October 6, 2014

Math
if f(ax) = af(x), f(x) = kx for some k. check: f(ak) = k(ax) = a(kx) = af(x) f(x+y) = k(x+y) = kx+ky = f(x)+f(y) So, since f(1) = pi, f(x) = pi*x f'(-1) = pi In fact, f'(x) = pi for any x.
October 6, 2014

Math- AP Calc
3x+xy+4y=8 3 + y + xy' + 4y' = 0 y'(x+4) = -(y+3) y' = -(y+3)/(x+4) y" = -[(y')(x+4)-(y+3)(1)]/(x+4)^2 = -[-(y+3)/(x+4)*(x+4) - (y+3)]/(x+4)^2 = -(-3-y-y-3)/(x+4)^2 = (2y+6)/(x+4)^2 check: 3x+xy+4y=8 y = (8-3x)/(x+4) y' = -20/(x+4)^2 y" = 40/(...
October 6, 2014

Math Proof
well clearly, since b_n is between 0 and a_n, as a_n->0, so does b_n. Not sure (b) follows. There must be some other conditions on the sequences.
October 6, 2014

word problems
since time = distance/speed, d/(12-2) = d/(12+2) + 1 d = 35 miles check: 35/10 = 3.5 35/14 = 2.5
October 6, 2014

clemson
If each pen is x by y, with the x side parallel to the river, then 6x+4y = 1680 a = 3xy = 3*x(1680-6x)/4 = (2520x-9x^2)/2 This is just a parabola with vertex (hence maximum area) at x = 140 So, each pen is 140 by 210 As usual, the fencing is divided equally between lengths and...
October 6, 2014

Math
not unless i√12 = √12 I think you meant 4±√-12 = 4±i√12 If so, then you are correct
October 6, 2014

Geometry
Now, if you meant to shift it 3 left and 8 down, then (8,3)+(-3,-8) -> (5,-5)
October 6, 2014

Geometry
singular is vertex, not vertice. Grr. (8,3) + (x-11,y-11) -> (x-3,y-8)
October 6, 2014

math
$591.12/72hr = $8.21/hr
October 6, 2014

Algebra
2x + 6/x = 79/5 10x^2 + 30 = 79x 10x^2 - 79x + 30 = 0 (5x-2)(2x-15) = 0 ...
October 6, 2014

Pre-Calc/Trig...
y = (x^2-4x+4) - 5+4 = (x-5)(x+1)
October 6, 2014

math
3(u-2) = 4(u+3) 3u-6 = 4u+12 u = -18 check: -20/-15 = 4/3 yes
October 6, 2014

Math, ASAP Please
Looks like D to me. Sheesh!
October 6, 2014

Calculus
depends on where the man is. If the man's distance is x, and the shadow has length s, then (x+s)/15 = s/6 Now just differentiate and plug in the distance when you finally deign to include it.
October 6, 2014

Timerate problem(calculus)
v = 1/3 pi r^2 (2r) = 2/3 pi r^3 at r=8, dv/dt = 2 pi r^2 dr/dt Now we just have to decide what "at what rate is the increasing" means
October 6, 2014

math
because 1/5 = 5^-1
October 6, 2014

ALGEBRA
It will take x days, where 1/x = 1/10 + 1/12
October 6, 2014

Maths
Apparently the sides are in the ratio b = 3/5 (a+c) c = 1/7 (a+b) a^2 = 144 a,b,c = 12,9,3 so, area = 144+81+9 = 234
October 6, 2014

Maths
If the bottles cost $x each, then 7x + 13.20 = 10x
October 6, 2014

geometry
(40-2*2)(20-2*2) = ?
October 6, 2014

Math
4/7
October 5, 2014

Math
no way to tell. How tall is the human?
October 5, 2014

Algebra
well, just plug in the points: a|1-b|+c = 4 a|3-b|+c = 8 a|8-b|+c = 3 a = -2, b = 17/4, c = 21/2
October 5, 2014

Algebra
a good site for long division is calc101.com Click on the long division button, and you can see all the details.
October 5, 2014

Calculus
As you can see from the graphs at http://www.wolframalpha.com/input/?i=plot+y%3De^%282x%29%2C+y%3D2x you missed the mark. So, let's see what happened. At the point (x,y) on the curve, the slope is 2e^(2x). A line with slope 2e^(2x) through the origin: e^(2x)/x = 2e^(2x) x...
October 5, 2014

math factoring
2x^4+12x^3-18x^2-108x 2x(x^3+6x^2-9x-54) Now use grouping 2x(x^2(x+6)-9(x+6)) 2x(x^2-9)(x+6) 2x(x-3)(x+3)(x+6)
October 5, 2014

Math
g'(x) = f(x^2) + xf'(x^2)(2x) = f(x^2) + 2x^2 f'(x^2) So, at x=2, g'(2) = f(4) + 8f'(4) = 4+8(-3) = -20 g(2) = 2f(4) = 8 So, now we have a point and a slope: L(x) = -20(x-2) + 8 = -20x+48
October 5, 2014

Math
A = 4pi r^2 dA = 8pi r dr Now plug in the numbers. Recall that % error is dA/A * 100
October 5, 2014

math
Hint: The only common divisors of 24 and32 are 2,4,8
October 5, 2014

9th grade algebra
Are you German? What's With All The Capitalization? The lope of the line is (190-120)/2 = 35 y = 50 + 35x
October 5, 2014

Math
at depth y, the radius of the water surface is r = (10/22)x = 5/12 x So, at depth y, the volume of water is v = 1/3 π (5/12 y)^2 = 25/432 π y^2 dv/dt = 25/216 π y dy/dt 30 = 25/216 π (14) dy/dt 30 = 5.08 dy/dt dy/dt = 5.89 ft/min As always, check my math.
October 5, 2014

statistics
Seems to me just like drawing from a pack of cards without replacement. p = 136/500 * 135/499 * 134/498 = 0.0198
October 5, 2014

solve long divison polynomials
A good site for long division is ath calc101.com Just click on the "long division" tab to see all the details, in proper formatting.
October 5, 2014

cobet, maths
Umm, didn't you just say that 33 like both?
October 5, 2014

calculus
First off, I suspect a typo. Why have two y^2 terms? I figure you meant x^2 + 4xy +4y^2=40 Just do things term by term, and don't forget the product rule: 2x + 4y + 4xy' + 8yy' = 0 y'(4x+8y) = -(2x+4y) y' = -1/2 Weird, huh? Not if you note that x^2 + 4xy +...
October 5, 2014

math
Ummm. First off, what do M and O have to do with the length of AB?
October 5, 2014

Math
4x^2+4y^2-8x-20y+13=0 rearrange things a bit and you get 4x^2-8x + 4y^2-20y = -13 4(x^2-2x) + 4(y^2-5y) = -13 Now complete the squares: 4(x^2-2x+1) + 4(y^2-5y+25/4) = -13 + 4(1) + 4(25/4) 4(x-1)^2 + 4(y - 5/2)^2 = 16 (x-1)^2 + (y - 5/2)^2 = 4 Now does it look familiar?
October 5, 2014

Math
what's to solve? You have just defined a function.
October 5, 2014

physics
The situation can be modeled as though the 1st tank were stationary, and the 2nd tank were retreating at 20 m/s. The horizontal and vertical components of the shell's speed at firing are x: 43.4 m/s y: 246.2 m/s So, the height of the shell is h(t) = 246.2t - 4.9t^2 It hits...
October 5, 2014

Algebra
father's age is f. My age is m. (f-4) = 4(m-4) f+m = 53 Now just solve for f and m.
October 5, 2014

Pre-Calc
well, it's just f(x)/g(x) = (1/x)/(x^3) = 1/x^4 And I'm sure you can figure the domain. It's where the denominator is not zero.
October 5, 2014

Math
clearly, it's b and c try dividing out the x^2 factor
October 5, 2014

Calculus
You have ∫√(u^2-a^2) du, so set u = a secθ du = a secθ tanθ u^2-a^2 = a^2 tan^2θ so it becomes ∫ (a tanθ)(a secθ tanθ) dθ = a^2∫secθ tan^2θ dθ = a^2∫sec^3θ - secθ dθ Now, we all...
October 5, 2014

Calculus
well, if y = sin^2(u) y' = 2 sinu cosu u' u' = ln3 3^x y' = 2ln3 3^x sin(3^x) cos(3^x) = ln3 3^x sin(2*3^x) I think you got some of your 3's mixed up as powers of sin. You appear to have taken the derivative of sin^3 (3^x)
October 5, 2014

Algebra 2 (Please, help me!)
Take |x| shrink it horizontally by a factor of 2: |2x| shift it down 3: |2x|-3 Now shrink it vertically by a factor of 4: (|2x|-3)/4 http://www.wolframalpha.com/input/?i=plot+y%3D|x|%2C+y%3D%28|2x|-3%29%2F4
October 4, 2014

Math
Since the border is on both sides, 5 + 2(2 1/4) = 9.5 7 + 2(2 1/4) = 11.5 2(9.5+11.5) = 42
October 4, 2014

Math
X^2+4x=10 x^2+4x+4 = 10+4 (x+2)^2 = 14 x+2 = ±√14 x = -2±√14
October 4, 2014

Math
that will of course be x miles where 100+.60x = 50+.80x
October 4, 2014

algebra
How could a quadratic be anything like a linear function?
October 4, 2014

algebra
You could think of it as a shifted parabola, where 2x+3(x-2)^2 = 3(x-2)^2 + 2(x-2) + 4
October 4, 2014

algebra
Is there a question in there somewhere?
October 4, 2014

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