Friday
August 29, 2014

Posts by steve


Total # Posts: 24,466

algebra
(x^5+x^2-3)(x^3-1) = x^8-3x^3-x^2+3 Now subtract -3x^3+x^2-4x and you get x^8-2x^2+4x+3 Now subtract 2x^2-4x and you get x^8+3 So, the whole thing is just (x^5+x^2-3)(x^3-1)-(-3x^3+x^2-4x)-(2x^2-4x)
May 26, 2014

Math
x is the total amount added. Since you get x=10, that means that 5m was added on each side. I'm interested in how you made this calculation: (10+x)(20+x)=600 200+10x+20x+4x^2=600 Where did the 4x^2 come from? looks like answer analysis to me. In addition, you did not solve...
May 26, 2014

Math
what is h when d=0? As you know the vertex of a parabola is where d = -b/2a = -4.4/-.88 So, figure h for that value of d. What is h when d=14? Or, how far away is the ball when h=0 (it hits the floor)?
May 26, 2014

Precal
(a) x(t) = 0 (since it went straight up) y(t) = 75 + 76t - 16t^2 (b) Just plug in t=2
May 26, 2014

Precal
(a) If you got the equations, answering the last 4 questions should be no sweat. (b) the ball is in the air while y(t)>0.That is, solve for t when y=0. (c) Knowing how long it took to hit, plug that into x(t). (d) y(t) is just a parabola. As usual, the vertex (where the ...
May 26, 2014

Precal
boarding at t=0, the height y at time t minutes is y = -60cos(pi/6 t) + 6 Now just start plugging in your numbers.
May 26, 2014

Precal
since the horizontal speed does not change, we have the usual x(t) = 150 cos 30° t y(t) = 150 sin 30° t - 16 t^2 The rest is downhill from here
May 26, 2014

Math, grade 10
except, don't make my typo. Better say x+y = 17
May 26, 2014

Math, grade 10
follow the same logic I used in your previous post: x+y = 18 x^2+y^2 = 185 go for it
May 26, 2014

Math, grade 10
x+y = 18 x^2 + 6y = 163 now substitute for y: x^2 + 6(18-x) = 163 x^2 - 6x + 108 = 163 x^2 - 6x - 55 = 0 (x-11)(x+5) = 0 x=11 and y=7
May 26, 2014

math
slope = rise/run, so 1.9 = 4/run run = 4/1.9
May 26, 2014

math
slope = rise/run = 5/15
May 26, 2014

math
No, x=5 is not correct. The solution set to an inequality is an interval, not just a single point. Your logic should have been: -5(x-7) < 15 -5x+35 < 15 -5x < -20 x > 4 You could have checked your answer to see that x=5 works, but it is not the only number which ...
May 26, 2014

Algebra
Not sure what a 2x3 matrix has to do with coordinates. Can you splain a bit, please?
May 26, 2014

Math
7s/1320ft * 1313ft = 6.96 s assuming instant change in velocity. Assuming a constant acceleration, 1/2 a*49 = 1320, so a = 53.877 ft/s^2 Now, to get 1313 ft using the same acceleration, we have 53.877/2 t^2 = 1313 t = 6.98 s
May 26, 2014

algebra
3 21 (3,21) -3 0 (-3,0) I think. Hard to say just what you are after.
May 26, 2014

math
h/100 = tan 24
May 26, 2014

Algebra 1--Please, help me!
#1 we have n calculators that cost c each. Since nc = k is constant, 24*60 = 80n #2 Actually, the cost must be a positive integer divisor of 75, since the number of packages must be an integer. #3 well, you have the formulas, and you want the ratio scone/scyl = (πrl + &#...
May 26, 2014

geometry math help
(a) two layers means 24 cans per layer. The cans are 10 cm across, so the 46x60 dimensions of the box allow for that many cans. The height of the box will accommodate the two layers. (b) You know the way to compute the volume of the box. Now, just subtract 48 times the volume ...
May 26, 2014

math
no idea. what does the pattern represent? How many more terms are to be considered? Ans why the ?? marks around the 20?
May 26, 2014

trigonometry
the angle is x, where sin x = 50/120
May 26, 2014

business math
just askin', but did you complete the table?
May 25, 2014

business math
just solve 2.903 t - 1.98 = 18 when you get t, add that to 2000 such bogus wordage. 4 <= t <= 9 is the condition.
May 25, 2014

Cosine Law
At 12:00 the hands are together After h hours, the hour hand has gone h/12 * 360 degrees After m minutes, minute hand has gone m/60 * 360 degrees 9:30 = 9.5 hours :30 = 30 minutes So, the hour hand has gone 9.5/12*360 = 285° and the minute hand is at 180° So, the angle...
May 25, 2014

Cosine Law
sinB/b = sinC/c that will get you B Then A+B+C=180 gets you A a^2 = b^2+c^2 - 2bc cosA gets you A. Then, b/sinB = c/sinC = a/sinA gets you A and B
May 25, 2014

3D Shapes & Scale
a 2m cube occupies 8 times the volume of a 1m cube. I assume the trailer is enclosed, so the volume makes a difference. So, what's 128/8?
May 25, 2014

trig
h/65 = sin 32
May 25, 2014

Earth Science Regents!!!
It is clearly #2. Since both observations were made at the same time, the orbit traveled by the planet can have nothing to do with it. Only separate observations at different times could indicate how the earth has moved. If the earth were flat, the star is so distant that all ...
May 25, 2014

math
well, that's 2(1/2) + 2/5 = 1 + 2/5 = 7/5
May 25, 2014

more logarithms help!
just plug in your values: 24000(1-0.15)^n = 2500 Now solve for n. First step is .85^n = 2500/24000
May 25, 2014

logarithm math help
log(x^n) = n*log(x) log(u/v0 = log(u) - log(v) Now go for it.
May 25, 2014

Math binomial formula and sequence
Almost: C(8,4)(2x)^4(-3)^4 90720x^4 ar^3 = 16 ar^6 = -128 r^3 = -8 r = -2 so, a = -2 a_n = -2*(-2)^(n-1) = -(-2)^n S15 = 15/2 (2*8+14*4) = 540
May 25, 2014

Math - Ratio
(a) 2.5km/10^4 = 2.5*10^5cm/10^4 = 25 cm .5cm:2.5km = .5:2.5*10^5 = 1:5*10^5 = 1:500,000 Just as a check, the 1:10,000 scale used 25cm, and .5cm is 1/50 of that, so the scale should be 1:500,000
May 25, 2014

Calculus
If you are assuming a parabola, then a little work will show that the equation is y = ax^2+bx+c 2500a-50b+c = 50 2500a+50b+c = 70 a(-b/2a)^2 + b(-b/2a) + c = 47 y = 1/200 x^2 - 1/5 x + 47 and the vertex is at (20,47) Now, the length of cable is thus s = ∫[-50,50] √...
May 25, 2014

Math - Logarithms
(a) x^5 = 100, so x = 100^(1/5) (b) I assume you mean 3^(x+5) = 81 we know that 3^4 = 81, so x+5 = 4 (c) log (4x+2)/2 = log 6x the logs are equal, so we just have (4x+2)/2 = 6 I guess you can probably handle that one, eh?
May 25, 2014

Geometry
review the description of a circle with center at (h,k) and radius r: (x-h)^2 + (y-k)^2 = r^2
May 25, 2014

Precalculus
4x^2-y^2-24x-10y+11=0 4(x^2-6x) - (y^2+10y) = -11 4(x^2-6x+9) - (y^2+10y+25) = -11 + 4(9) + 25 4(x-3)^2 - (y+5)^2 = 50 Better check to see what you lost while completing those squares.
May 24, 2014

Algebra 2
a = -2 r = -2 so, T20 = -2*(-2)^19
May 24, 2014

Math
I also get 1/2 * 1/2 = 1/4 since the two events are independent.
May 24, 2014

Algebra 2
If the box originally had side s, then the new box has side s-6, since 3" was cut off each corner. The height of the box is just the 3" that was cut off. So, s(s-6)^2 = 675 Now, just by inspection, 675 = 3*225 = 3*15^2 So, the box now has sides of 15, and height=3 ...
May 24, 2014

Math - eh?
since T3 = T1 * r^2, r = 3 No idea what "124 of the fifth" means
May 24, 2014

Math - Linear Equations
T = k√L so, T/√L is constant. (a) .63/√9 = T/√25 (b) .63/√9 = 1.5/√L
May 24, 2014

Algebra
since time = distance/speed, d/(12-5) + d/(12+5) = 3 now just solve for d. Assuming the round trip takes 3 hours.
May 24, 2014

Algebra
Assuming they both work the same time, Alma works 4/3 as fast as Kevin, so she does 4/7 of the work, or 57% Or, you can find how long it takes to do the whole job together: 1/x = 1/4 + 1/3 x = 12/7 So, in 12/7 hours, Alma does 1/3 * 12/7 = 4/7 of the work.
May 24, 2014

Algebra
they have 1/4 the distance to go. They have walked 3/4, or 3 times that far.
May 24, 2014

arithmetic
Nice homework dump. Can you show any effort on any of the problems?
May 24, 2014

Trig
The nth term has 2^-n, so the ratio is 2^-1 = 1/2 Did you try listing the first few terms? That would have made it clear that 2 was not the ratio.
May 24, 2014

Math - Linear Equations
total trucks: x+y = 8 total loads: 10x + 5y = 70 I expect you can solve that with little difficulty.
May 23, 2014

Algebra 1--Please, help me!
The question still is poorly worded. What is the "side" of a roof? I expect we are looking at the end of the building, at the cross-section area. The triangle has area a1=b2*h/2 The trapezoid has area a2=(b1+b2)*h/2 The ratio of areas is thus a1/a2 = (b2*h/2) / (b1+...
May 23, 2014

Math - Variation
T = kd^4n^2 if we replace n by 2n and d by d/2, we have T' = k(d/2)^4(2n)^2 = kd^4n^2/4 = T/4
May 23, 2014

geometry
12000/x = sin 32°
May 23, 2014

HELP MATH !!
correct
May 23, 2014

HELP MATH !!
If there's a constant term, that just plugs right in. Melanie always has $5.00 for supplies. If there's a cost which is "per" unit, that is the slope of the line. Each new unit adds some fixed amount. Melanie gets $4.50 for each new hour worked. So, y = 4.50x...
May 23, 2014

algebra
Better recheck your numbers. C is correct. If the attendance was equal 15x + 76 = –x2 + 36x – 4 x^2-21x+80 = 0 (x-5)(x-16) = 0
May 23, 2014

math
and we have a winner!
May 23, 2014

Algebra 1--Please, help me!
(a) want a ratio? Just plug in the numbers for a fraction (1/2 b^2 h) / ((b1+b2)/2 h) = b^2/(b1+b2) For (b), just substitute in new values and see how the ratio changes. By the way, having b^2 for one figure and b1+b2 for the other plays havoc with the units. Better check your...
May 23, 2014

algebra
pick two x values, figure the y values there, and plot the points. Then draw a line between them. Easy points to pick are where x=0 or y=0. 2x = -10y (0,0) is on the line. If x=5, y=-1, so (5,-1) is on the line Plot those two points and draw a line through them. x+5y=3 (3,0) ...
May 23, 2014

Math - vastly incomplete
!!!
May 23, 2014

algebra
1/2 is 2/3 as big as 3/4 So, R will be (3/2)^2 = 9/4 * 12 = 27 ohms
May 23, 2014

Math
you are correct. Just use whatever type of graph you feel most clearly depicts the data collected. Not a frequency table. That is not a graph. It might be a part of the description, though.
May 23, 2014

math last set up
The angle is θ, where tanθ = (618-10)/90
May 22, 2014

math
you can play around with these things at http://davidmlane.com/hyperstat/z_table.html
May 22, 2014

math
Draw a diagram. If the bottom of the balloon is at height x and the top of the balloon is at height y, then x/32 = tan46° y/32 = tan56° The height of the balloon is just y-x, or 32tan56° - 32tan46° = 32(tan56°-tan46°)
May 22, 2014

Algebra
not sure just what you want. 9C6 = 9C3 = 9*8*7/1*2*3 = 84 6C4 = 6C2 = 6*5/1*2 = 15 3C1 = 3/1 = 3 More formally, 9C6 = 9! / (9-6)!6! 6C4 = 6! / (6-4)!4! 3C1 = 3! / (3-1)!1!
May 22, 2014

Math - Literal Equations
area of base = 9, so 9*height = 144 height = 16
May 22, 2014

algebra 2
don't know what f and g are, but (f+g)(x) = f(x)+g(x) plug in your value for x and add the two functions there.
May 22, 2014

geometry
θ is the angle that has sinθ = 12/452
May 22, 2014

Geometry Help!!!
I don't see any question here, but if you label the triangle's vertices as PKF, with P as the right angle, then the library sits at L, where ∆PKF ~ ∆LFP ~ ∆LKP You can get the length of PL or FL or KL from those ratios.
May 22, 2014

math
d/24 = cos 15°
May 22, 2014

college calculus
or, you can think of it like this: every half-life, 1/2 of what was there is gone. So, the amount left after t half-lives is (1/2)^(t/5730) So, we want t when (1/2)^(t/5730) = .45 t/5730 = log(.45)/log(.5) = 1.152 That is, it takes 1.152 half-lives to reduce to 45% So, t = 1....
May 22, 2014

Math
1000050 - 5*85000 = ?
May 22, 2014

Calculus
(100*7 + 300*2 + 200*6)/15 = 166.67 It always helps if you show your own work - then it's possible to point out the mistake, if any.
May 22, 2014

maths
.05*25000 + 275 = ?
May 22, 2014

CHEMISTRY
Hard to say. If there's an excess of Mg, then the N2 is the limiting reagent. If there's plenty of N2 around, then the Mg limits the reaction.
May 22, 2014

Language Arts Grade 8
You can find the table of contents at amazon.com: http://www.amazon.com/Popol-Vuh-Definitive-Edition-Glories/dp/0684818450#reader_0684818450
May 22, 2014

math
.05 * 25000 = ? Since you mention two increases, I'm not sure just what is to be done. I would not expect the COL increase to include the merit increase.
May 22, 2014

geometry
There is no apothem. Only regular polygons have one. In this case, the lateral area is the three faces of dimensions 3x6, 4x6, 5x6 The volume is v=Bh where B is the area of the base, 1/2 (3)(4)
May 22, 2014

Algebra 2
If we try to solve this algebraically, we run into trouble. x^2 + y^2 = 1600 x^2 + (1/40 (x-40))^2 = 1600 x^2 + 1/1600 (x-40)^4 = 1600 (x-40)^4 + 1600x^2 = 1600^2 Now, that's a hard one. However, if you examine the two equations, you see that the first is a circle of ...
May 22, 2014

Math please check my answer?
Not B, that's for sure. The x-intercept is where y=0. Plug that in and you get 6x=30 Similarly, if x=0, we get 11y = 30 The values in B are the reciprocals of the true answers.
May 22, 2014

appliance repair
I guess the context of the subject, the question and its choices would indicate that the class is in electricity or electronics, and not physics. Not much call for Electric Field strength in appliance repair... :-)
May 22, 2014

physics
conserve momentum: .02*80 = 100v
May 22, 2014

English
#2. read up on restrictive qualifiers. They don't use the comma.
May 22, 2014

math
Back to the drawing board. Try 1B 2B 4C 8A 9D are you just guessing here? I'm especially intrigued at #2, since I gave you the answer! It would have helped had you actually shown your work. Then I might have been able to show you where you went wrong.
May 22, 2014

math
#1. Interesting. 1/5 of 60 is 12. So I'd be interested to know how you figure a 2/5 increase is only $9. #2. Interesting. 4 days at $40/day would only be $160, and she paid less than that. 12.5 cents is about 10% of 380 or about $40 So, an estimate would be about $200. How...
May 22, 2014

Maths
No, a=2b a+b = 40 2b+b = 40 ?? Not an integer solution Also, you started out saying a=boys and b=girls. Then you say b=2a, but that's not correct. The whole problem looks mishandled.
May 22, 2014

Algebra
this is just a quadratic, so the max is reached at x = -b/2a = -500/-50 = 10
May 22, 2014

Math
the new balance is just old balance + finance charge - payment.
May 22, 2014

Calculus
f(x) = 2x^3 - 3x^2 - 72x + 7 f'(x) = 6x^2 - 6x - 72 = 6(x^2-x-12) f"(x) = 12x-6 = 6(2x-1) f'=0 at x= -3 and 4 f"=0 at x = 1/2 Now it's easy to answer the questions. f is increasing where f' > 0 f is concave up where f" > 0 no asymptotes, so...
May 22, 2014

Algebra
(9x+1)(2x-3) = 0
May 21, 2014

Algebra
(1/2)^3
May 21, 2014

Math
6+2x = 48 Looks like 21 DVDs. Naturally, the total cost would be $48, since the 2nd plan always costs that.
May 21, 2014

furthermathematics
the horizontal distance is x(t) = u cosθ t The time taken to go 20m is thus t = 20/(u cosθ) The trajectory is y(t) = u sinθ t - g/2 t^2 We know that y=0 at 0 and 20/(u cosθ), so the max height is reached at 10/(u cosθ). So, u sinθ * 10/(u cosθ...
May 21, 2014

Math 6 gemoetery
Good call, Damon. By rounding down to 90 I neglected the rather sizable underestimate of 2.47 by 2.00.
May 21, 2014

Math 6 gemoetery
Rounding each value to the nearest single-significant-digit approximation, that would be 90x60x2 I'd choose that instead of 100*60 because in that case both values are rounded up, making the estimate too high.
May 21, 2014

Algebra
2x+5 > 1 x > -2 So, of the 10 numbers, how many are greater than -2?
May 21, 2014

math ~dont know all but check some~ pls help!!!
#1 x^2+2x+4 can be written as x^2 + x(2) + 4*1^2 I think that the best choice would be 1 big square, 1 tall rectangle, 4 little squares #2 –3f^2 + 4f – 3 + 8f^2 + 7f + 1 just collect terms of the same power (-3+8)f^2 + (4+7)f + (-3+1) 5f^2 + 11f - 2 #3 (2x^2 + 6x + 1...
May 21, 2014

maths/permutation and combination
You have to have the 2 or 3 as the first digit. After that, the other 3 digits can be done in 3! = 6 ways. So, the total is 2*3! = 12
May 21, 2014

Calculus
the gradient is the slope of the tangent to the curve. y' (x) gives the slope of the tangent for any value of x. So, at x=0, y'(x) = 2-0 = 2, so the gradient is 2 at the point (0,2) See the graphs at http://www.wolframalpha.com/input/?i=plot+y%3D2x-x^2%2Cy%3D2x
May 21, 2014

Calculus
y = 2x-x^2 y' = 2-2x so, where is 2-2x = 2?
May 21, 2014

maths
these are standard values. plug them in; what do you get?
May 21, 2014

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