Friday
April 18, 2014

Posts by steve


Total # Posts: 21,739

physical science
seconds

science
even if you don't know #1, it's evident from the other questions that this is an exercise set involving matrices. #10: a=2 Now, what ideas do you have on the others?

Math
sorry; that's the angle between the diagonal and a side of the rectangle. so, draw a diagram, and the angle you want is Ø, where 2θ+Ø = 180

Math
tanθ = 130/170 or, for the other angle, tanθ = 170/130

kinridg
there are 1/8 left, so that's 3 half-lives

chemistry 101
How many grams of bromine are in 1.57 grams of phosphorus tribromide?

Math, Please Help!
he has n/3 + 2 he wants 3n - 2 to get the 3n, he needs to multiply by 9. That will give him 3n+18 So, then he needs to subtract 20.

Calculus
Hmmm. I get 10x-15y = 75 http://www.wolframalpha.com/input/?i=plot+x^2%2B4y^2%3D36+and+y%3D3+and+10x-15y%3D75

Calculus Help and Check
x^5(x + y) = y^2(9x − y) 5x^4(x+y) + x^5(1+y') = 2yy'(9x-y) + y^2(9-y') 5x^5+5x^4y + x^5 + x^5y' = 18xyy' - 2y^2y' + 9y^2 + y^2y' y'(x^5 - 18xy - 3y^2) = 9y^2 -6x^5 - 5x^4y y' = (9y^2-6x^5-5x^4y)/(x^5-18xy-3y^2) you were close, but mus...

algebra
ummm. No 1.1(5) = 5.5 5.5+1.7 = 7.2 c = 1.1d + 1.7 Did you even try your formula against the data?

algebra
If the formula is c=ad+b, then 5a + b = 7.20 9a + b = 11.60 Solve for a and b. Or, note that as the distance increased by 4, the cost increased by 4.40 So, the slope is 1.1 That eliminates two of the choices right away. Now just see how much extra there is in each case when mu...

Chemistry
half the concentration means twice the volume. so, add another 600.0 mL of H2O

Math
slope is y-change/x-change so, as x changes by 2 each time, y changes by -3. So, the slope is ...

I need help (Physics)
PE = mgh = 28*9.8*159 KE = 1/2 mv^2 = 1/2 * 28 * 31.3^2 Because of friction, not all of the PE changed to KE. Subtract to see how much energy was lost.

algebra
Try actually plugging in the points to see which equation fits! Or, arrange the points from left-to-right: (-4,-3) (-2,1) (0,5) (1,7) (3,13) as x changes by 2, y changes by 4 (except for the last one - typo?) It appears that none of the choces will work.

Mathematics
60 = 14*3 + 18 So, 14 will do the trick if they have 3 chickens each.

math
(x-6)(x+3) = 0 for the product to be zero, one of the factors must be zero.

math
so, add up the taxes: .18+.124+.029 = .333 Since it's a quarterly return, .333/4 * 20640 = 1718.28 Now, how about showing some ideas on the others you posted?

Math
when the lines are the same. 2x-y = 5 Hmmm. a typo - no y term in the 2nd equation. Anyway, since there are 8x, the same line would be just 4 times the other. 8x - 4y = 20 Looks like a=10

Algebra
#1: N = {1,2,3,6,9,18} --------------- #3: subsets of {2,9} are {},{2},{9},{2,9} Now, how about showing some of your ideas on the other problems?

math
Hmmm. I think I mean 1 : 5/6 : 2/3

math
(2/5) : (1/3) : (1 - 2/5 - 1/3) 1 : 6/5 : 3/2

pragati
since angle B is a right angle, AB is the height of the trapezoid. So, the area is (16+40)/2 * √(41^2 - 40^2)

Calculus
(-4,185°) (-4,-75°) got any more?

math
best to use shells here: v = ∫[0,2] 2πrh dx where r = 3-x and h = y = x^3 v = 2π∫[0,2] (3-x)x^3 dx Simply polynomial, so just plug and chug.

pragati
a = (42+54)/2 * √(19^2 - 12^2)

math
You won't find any diagrams here, but division is just a shorthand way to subtract. 2.6/.4 tells you how many times you can subtract .4 from 2.6 without passing zero. 2.6 - .4 = 2.2 2.2 - .4 = 1.8 1.8 - .4 = 1.4 1.4 - .4 = 1.0 1.0 - .4 = 0.6 0.6 - .4 = 0.2 Now you must sto...

Calculus Help
#1: 2y y' = 2x + 0 #2: 2y y' + ay' = 2x + a + 0 just solve for y' in each case.

math
what's the smallest number that is a multiple of both 2 and 3? And for 8 and 10?

Algebra
slope is (-8-4)/(3 - -3) = -2 Now plug in the point-slope form: y-4 = -2(x+3) Now it's easy, right?

science pls help
correct. At least it appears you can match up the provided answers with the lists of choices...

science pls help
Looks like you need to brush up on one of the most basic and useful identities in mechanics: F = ma F(N) = m(kg) * a(m/s^2) 1 N = 1 kg-m/s^2 So, with that in mind, #1: F = ma = 40kg * 10m/s^2 = 400 kg-m/s^2 = 400N #2: F = ma = 60kg * 2m/s^2 = 120N Note that you can eliminate t...

Math
after n hours, 1+3+3^2+3^3 + ... + 3^n = (3^n - 1)/2 people have heard the joke. So, we want n such that (3^n - 1)/2 = 8500 3^n = 17001 n = 8.8666 hours = 8 hrs 52 min

Math
7*8*4 = 56*4 = 224 recall that using a variable, 7x * 8x * 4x = 224x^3 Now, using units, 7ft * 8ft * 4ft = 224 ft^3

Math
did you multiply the three dimensions? If so, what did you get? If not, what's the problem?

Math - Answer Check
I'd say #15 is right, since you were given 180,000 inches. 2.84 miles is close enough, IMO.

Math - Answer Check
#12. a mile is 5280 ft, not 5820 The rest look ok (including #15!)

MATH
1/5 is correct 1/4 may be correct, but only if there is exactly one white sweater in the bunch.

Pre-Calculus
r = 5sinθ r^2 = 5r sinθ x^2+y^2 = 5y x^2 + (y - 5/2)^2 = 25/4

Pre Calculus
rcosθ = 3 r = 3secθ

MATH
but 1 is not a prime. It is explicitly excluded from the list of primes.

Geometry
recall that if the legs of a right triangle are a and b, and the hypotenuse is c, then the Pythagorean Theorem states that a^2 + b^2 = c^2 So, the height of the triangle is 12 There are several commonly used right triangles which you would do well to commit to memory: 3-4-5 5-...

Geometry
5^2 + height^2 = 13^2

Which compound is made up of three elements?
Do you know how to count the elements in a chemical formula?

algebra
hint: y = -4/6 x + 2

math
Hmmm. of the 11 numbers, how many are NOT 23?

math
So, P(violet, pink, or blue) = V+P+B

math
assuming that what was meant is that the jar contains ONLY green and purple marbles . . . I think we can say that, but it's also possible that other marbles were not mentioned. Read Heinlein's Stranger in a Strange Land. One of the characters is a professional observer...

math
correct

Probability - Math
total junior or seniors / total students (.16+.24)/1.00 = .40 Those who live in the dorm: (.16*.30 + .24*.20)/1.00 = .096

Science
hint: both correct choices involve only water

math
now you're cookin' (aside from that pesky 32!)

math
ummm, 6+7+26+13 = ?

math
number 2 is ok #1. Come on! The numbers are 1,2,3,4,5,6 only FOUR is divisible by 4! P(4) = 1/6

math
If there are 6 numbers on the die, how many of them are multiples of 4? I think not 2. How many numbers are there from 16-23? Remember to count both 16 and 23. #3 ok

Calculus
well, x^2/(2logx) = x^2/log(x^2), so if you can figure out the limit of x/logx, you're ok. Since x->0 and logx->-∞, x/logx -> 0/-∞ = 0 -------------- e^-x -> 0 as x->∞, so the upper limit -> 0 e^0 = 1, so the lower limit -> 2

Math
well, the factors of 18 are 1,2,3,6,9,18 The -21 in the middle makes me think that 2,9 will be likely, so (4x+9)(x-2) gives +x nope (2x+9)(2x-2) gives +14 Hmmm. That pesky 4. So, (4x+3)(x-6) : -21x YAY!

Math
after the 1/3, she had 2/3 left 1/2 of that is another 1/3, so if she started out with x, x - x/3 - x/3 = 6 x = 18 check: she spent 6, had 12 left. she lost half of 12, or another 6, leaving her with just 6.

Math
yes

Math
assuming the velocity is as written, a = 3(2) = 6 If you meant 3(2t+1)^0.4, then a = 2.4/(2t+1)^0.6 as usual, s = 25 + 1/2 at^2 = 25 + 3t^2 or = 25 + 1.2(2t+1)^1.4 just plug in your values.

Calc Help :(((((
d/dx(x) = dx/dx = 1 So, how come you included it in d/dx (x+3) but not in d/dx (x-8)? Your work so far is correct. 3(x+3)^2(x-8)^5(d/dx(x))+5(x+3)^3(x-8)^4 3(x+3)^2(x-8)^5 + 5(x+3)^3(x-8)^4 Now factor out some stuff: (x+3)^2 (x-8)^4 (3(x-8)+5(x+3)) (x+3)^2 (x-8)^4 (8x-9)

math
find the factors. If any of them is zero, the product is zero. Sometimes the factors are hard to find, and sometimes there are none using just real numbers. For higher than quadratics, it starts to become necessary to use various numerical methods.

math
I would assume it means to divide each third into two pieces (presumably also equal halves)

math
avg speed is total distance divided by total time: (5+4)/(21+39) km/min = 9 km/hr That's a pretty good clip!

Science URGENT
Since 1 mole of S8 reacts with 4 moles of Cl2, .779 moles S8 will need 3.116 moles of Cl2, but you only have 1.410 moles Clearly the Cl2 is lacking here.

Science asap
#1 Looks like B to me D means that it doesn't rain till after the water has run off. Clearly it has to precipitate before the water is in the river.

Chemistry
It'd be Iron Nitrate, but more precisely, Iron (II) Nitrate

Ms Sue is an Angel
:-)

CALCULUS HELP
If we let u = 8x-3 v = 6x+7 then we can make the expression a little easier to read during the computational steps: f' = (5u^4*8*v^12-u^5*12v^11*6)/v^24 Now, you can cancel out v^11 top and bottom to get f' = (40u^4*v - 72u^5)/v^13 Now factor out 4u^4 to get f' = 4...

math patterns and rules
have you actually tried any of the proposed solutions?

algebra
hard to say, eh? what was the relation?

math/algebra
1 - 1/(x-1) - 2/(x+1)

math
First step -- talk to your teacher!

Math
20 times 10 = 200

Calculus
limit as x->2- = 5 limit as x->2+ = 5 since one-sided limits are the same, and f(2)=5, f is continuous Do you have to do the delta-epsilon limit proof?

Calculusmath
think. It's a circle. Invariant under rotation about its center.

Precalculus II
x = -5 + 11arccos(7^y-9) (x+5)/11 = arccos(7^y-9) 7^y-9 = cos (x+5)/11 7^y = 9 + cos (x+5)/11 y = log7 (9 + cos (x+5)/11) you know that sin π/3 = √3/2 so, 2kπ + π/3 or (2k+1)π - π/3 or (2k+1)(π/2)±(π/6) 1+cos(3x-π/4) = 1/2 c...

math
(x-6)(x+3)

Calculus
as usual, draw a diagram and you will see that if θ=0 when x=0, tanθ = x/4 so, sec^2θ dθ/dt = 1/4 dx/dt Now, you have θ and dθ/dt, so just solve for dx/dt

Calculus
At time t, using the law of cosines, d^2 = (7t)^2 + (5t)^2 - 2(5t)(7t)cosπ/4 = 74t^2 - 35√2 t^2 = (74-35√2)t^2 so, 2d dd/dt = 2(74-35√2)t Now, plug in your numbers to get d(15), and solve for dd/dt at t=15 Remember to use appropriate units

algebra
if so, y/x is constant 6.4/4 = 1.6 11.2/7 = 1.6 16/10 = 1.6 looks good, no?

Calculus
what you have tried is the volume when rotating the region about the x-axis. But, of course, the volume of a disk is pi r^2 dx, not pi r^3 dx In addition, your radius is 3-x, not y, since you are rotating about the line x=3, not y=0. So, if you want to use discs, you need to i...

Calculus- typo
64/6 + 8 + 20 - ( -64/6 + 8 -20 ) 64/3 + 0 + 40 184/3

Calculus
product rule and chain rule -- if y = uv y' = u'v + uv' Here u=csc^2 x and v = arccos(1-x^2) y' = -2 cscx cscx cotx arccos(1-x^2) + csc^2 x 1/√(1-(1-x^2)^2) * -2x kind of messy, no? well, recall that if cos u = 1-x^2, sin u = x, so we really have y = -csc...

math
13/150

Math
84 = pi * 36 * h now just solve for h same for the other

Calculus Help
just use the quotient rule and chain rule. If f = u/v f' = (u'v-uv')/v^2 f' = 5(8x-3)^4(8)(6x+7)^12 - (8x-3)^5(12)(6x+7)^11(6)]/(6x+7)^24 = -16(8x-3)^4(21x-31)/(6x+7)^13

math studies
The diagonals are perpendicular, and they bisect each other. So, you have 4 right triangles with legs 6 and 3.5 The diagonals bisect the vertex angles, so the angle is 2arctan(6/3.5)

Algebra
If a+b = c you cannot say that a^2+b^2 = c^2 √(9y - 196) + √196 = √49 √(9y - 196) + 14 = 7 √(9y - 196) = -7 But, √N is positive. So, you cannot have √(9y - 196) = -7 √x(√9 - 4/3) = √25 √x(3 - 4/3) = 5 √x(5...

Algebra
x=.10(100-x) x = 10 - x/10 11/10 x = 10 x = 100/11

Chemistry - incomplete
A good first step would be to get some H on the left . . .

Math
the difference is 32 votes Had 16 people voted differently, they'd both have had 228 votes. So, if at least 17 had voted differently, Susan would have won.

Algebra
There's no way that √28 + √63 + √175 = 6.06 You must have hit some wrong keys Just a rough approximation would be 5 + 8 + 13 = 26, not 6.06!

Algebra
#1 ok #2 ok if you meant √(6p+1) #3 √28 + √63 + √175 2√7 + 3√7 + 5√7 = 10√7 #4 √(2w+5) + 4 = √25 √(2w+5) = 1 2w+5 = 1 2w = -4 w = -2 #5 √18/√(8-3) 3√2 / √5 (3√10)/5 If you meant ...

Algebra
check the discriminant #1: b^2-4ac < 0, so no solutions #2: b^2-4ac = 0, so one solution

Algebra
let's say that f(x) = a√x + b Then we know that a√1 + b = -2 a√5 + b = 0 a(√5-1) = 2 a = 2/(√5-1) = (√5+1)/2 b = -2 - (√5+1)/2 = -(√5+5)/2 f(x) = (√5+1)/2 √x - (√5+5)/2 Somehow I don't think that's w...

Mathh
squares: 1 4 9 cubes: 1 8 27

math. plzz help
√(3^2+5^2) = √34 so the slant height is 5.8 √(10^2+4^2+10^2) = √216 = 14.7 √(14^2+3^2+4^2) = √221 = 14.9

Algerbra
factors of 18 which differ by 3 are 3 and 6, so w(w-6)(w+3)

Math
If Ling, suitcase, and backpack weigh x,y,z, respectively, then we have x = 3y y = z+20 x+y+z = 170 so, 3y + y + y-20 = 170 5y = 190 y = 38 So, Ling weighs 114 suitcase: 38 backpack: 18

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