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March 25, 2017

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Posts by steve

Total # Posts: 49,574

math
These are the 6 ways to pair up the vowels: AA EE AE AE AE EA EA EA EA AE EE AA Now consider the ways if you use each pair as a single letter. But consider duplicates.
March 13, 2017

math
It crosses the x-axis whenever sinx = -1/2. That is, whenever x = (2k-1)? + ?/6 x = 2k? - ?/6 for any integer k. If you just wanted the graph, why not visit any of hundreds of graphing sites, such as this one: http://www.wolframalpha.com/input/?i=1%2B2sinx
March 12, 2017

Math
distance = speed * time, so (3 1/2)*(1 1/3) = 7/2 * 4/3 = 14/3 = 4 2/3 miles
March 12, 2017

Algebra2
divide by 64 to get x^2/4 - y^2/16 = 1 Review your material on hyperbolas, and see whether you can see how to get the information shown here: http://www.wolframalpha.com/input/?i=hyperbola+x%5E2%2F4+-+y%5E2%2F16+%3D+1
March 12, 2017

Algebra2
What are the vertices, foci, and asymptotes of the hyperbola with the equation 16x^2-4y^2=64? What would the formulas be to find the answers?
March 12, 2017

Advanced Functions - oops
sorry. You did yours in minutes. He did his in seconds, but the ratio is the same.
March 12, 2017

Advanced Functions
You have figured the period in hours. Reiny did it in minutes, so his period is 6pi/60 = pi/10
March 12, 2017

Advanced Functions
see related questions below. If you're still stuck, show us your work and your sticking point.
March 12, 2017

Math
18" = 1.5 ft So, the area of the box is 2(3.5*1.5 + 3.5*2 + 1.5*2) = 30.5 ft^2 Or, using the Ph+2B, we have 2(3.5+1.5)*2 + 2(3.5*1.5) = 30.5 ft^2 Now add the 2.5 to get 33 ft^2 The first formula uses the fact that you have two sets of rectangular faces. The area of each ...
March 12, 2017

Math
what, you can't plug in t=15?
March 12, 2017

Maths
The area could also be considered using horizontal strips. In that case, each strip lies between the line and the curve, with no break in the boundary. Then the area is ?[0,27] (y/27 + 2)-?y dy = 27/4
March 12, 2017

Maths
You cannot just integrate on [0,2] to get the area. That ignores the part between the curve and the line on the interval [2,3]. That is ?[2,3] x^3-(27x-54) dx = 11/4 Add that to your area of 4, and you get 27/4
March 12, 2017

geometry
Where are P and Q in relation to K and N?
March 12, 2017

Mathematics
To start with, Construct a right angle. Bisect it. Measure off the lengths. Label the points. Then figure out what the heck angle "DE" is.
March 12, 2017

math
Suppressing all those trailing zeros, 25b + 10c <= 250 25b >= 50+10c b >= 5 c >= 7
March 12, 2017

Math
Draw a diagram. It should be clear that if B is h meters tall, (40-h)/10 = tan 26°
March 12, 2017

math
it is in simplest form if the numerator and denominator have no common factors.
March 12, 2017

Chemistry
Determine the Enthalpy of combustion of ethyne (C2H2) using the following enthalpies of formation; Data: DHf°(H2O)= -285.9kj/mol DHf°(2H2)= +226.7Kj/mol DHf°(CO2)= -393.5Kj/mol Equation; C2H2--------->CO2 + H2O
March 12, 2017

calculus
See here: http://www.intmath.com/applications-integration/5-centroid-area.php scroll down for a nice example, with steps for solution.
March 12, 2017

calculus
the volume of water is 10^2 * ? * 2.5 = 785.4 m^3 That much water weighs 785.4 * 1000 * 9.8 = 7696920 N The center of mass is 1.75m below the top of the pool, so the work required to lift it all is 7696920N * 1.75m = 13,470,000 J But, if you want to use calculus, consider a ...
March 12, 2017

physics
why do you say it is abnormal?
March 12, 2017

physics
(70.71i+70.71j)-(0i+100j) = 70.71i-29.29j
March 12, 2017

calculus
see related problems below.
March 11, 2017

Advanced Functions
cos(pi/2 - x) = sin(x) so, cos(?/2 - ?/10(t-5)) = sin(?/10(t-5)) you should probably simplify that.
March 11, 2017

Math
-4 < x < 5 -16 < 4x < 20 -11 < 4x+5 < 25 so, ...
March 11, 2017

Math (Stats)
I agree
March 11, 2017

Math (Stats)
So, what does the correlation coefficient tell you about the accuracy of the regression line?
March 11, 2017

geometry
what, you can't plug in values? A(1) = -2+(1-1)(-2.2) = -2 A(2) = -2+(2-1)(-2.2) and so on hint. Just keep subtracting 2.2 to get the next term.
March 11, 2017

Maths
To be divisible by 4, the last two digits must be a multiple of 4. Using those digits, the only possibilities are 12,16,28,56,88 There are 5^5 possible 5-digit numbers. Of those, 5^3 * 5 = 5^4 end in those digits. So, 5^4/5^5 = 1/5 of the numbers will be divisible by 4. Adjust...
March 11, 2017

algebra
z = kyx^2 so, z/(yx^2) = k is constant. So, you want x such that -96/(2x^2) = -84/(7*4)
March 11, 2017

algebra 1
Take a look here. It's almost the same. http://www.jiskha.com/display.cgi?id=1489212302
March 11, 2017

math
well, technically, there is no smallest number. You could also multiply any perfect-square fraction with a larger denominator. That will give you an even smaller result. Not an integer, but a fraction as small as you like. just sayin' ...
March 11, 2017

math
you need all even exponents for a perfect square. 5^3 7^3 3^4 * 5*7 = 5^4 7^4 3^4
March 11, 2017

Math
geometric, not arithmetic A6 = ar^5 = 9375 A4 = ar^3 = 375 A6/A4 = r^2 = 9375/375 = 25 r = ±5 A9 = A6*r^3 = 9375 * ±125 = ±1171875
March 11, 2017

maths/calculus damon,steve,reiny help steve
x^3 dy/dx + 3y^2 = xy^2 x^3 dy = y^2(x-3) dx dy/y^2 = (x-3)/x^3 dx -1/y = -1/x + 3/(2x^2) + c 1/y = (3-2x)/(2x^2) + c y = 2x^2/(2x-3+cx^2) y(1) = 1, so 2/(c-1) = 1 c = 3 y = 2x^2/(3x^2+2x-3)
March 11, 2017

Math
as with any quadratic ax^2+bx+c, the vertex lies on the axis of symmetry, at x = -b/2a In this case, that is x = -1 f(-1) = -1 so the vertex is at (-1,-1) Or, you can complete the square to find the vertex: f(x) = 2x^2+4x+1 = 2(x^2+2x)+1 = 2(x^2+2x+1)+1-2 = 2(x+1)^2 - 1 Recall...
March 11, 2017

math
or, 3x+7x = 210 10x = 210 x = 21 dogs = 3x = 63 cats = 7x = 147
March 10, 2017

math
The above answer is clearly wrong, since the total animals is only 210, not just the dogs. d/c = 3/7 7d = 3c d+c = 210 3d+3c = 630 3d+7d = 630 10d = 630 d = 63 so, c=147
March 10, 2017

Math
f(x) = -(x^2+x-2) = -(x+2)(x-1) The roots are at -2 and +1 So, the vertex and the axis of symmetry are midway between the roots, at x = -1/2 Now just find the y-coordinate of the vertex.
March 10, 2017

Calculus - Derivatives
x^2 + 5y^3 = 8 2x + 15y^2 y' = 0 y' = -(2x)/(15y^2) y" = - [(2)(15y^2)-(2x)(30yy')]/225y^4 = (60xyy'-30y^2)/(225y^4) = (2xyy'-y^2)/(15y^4) = (2xy'-y)/(15y^3) = 2(2x(-(2x)/(15y^2))-y)/(15y^3) = -2(4x^2+15y^3)/(225y^5)
March 10, 2017

Math
the right one
March 10, 2017

pre calc
#1 Po = 1000 Since P(1) = 1.8*P(0), P(t) = 1000*1.8^t To check this, 1000e^(k) = 1800 k = ln(1.8) 1000e^(ln(1.8)*t) = 1000(e^(ln1.8))^t = 1000*1.8^t Or, if you prefer the base e, P(t) = 1000e^(0.5878t) I expect you can handle the rest, now, ok?
March 10, 2017

pre calc
Surely you can just plug in your numbers. #1: N(4) = 1000*e^.04 #2: 1000*e^.01t = 1700 #3 e^.01t = 2
March 10, 2017

geometry
Nope. 360/n corresponds to the arc subtended by each side: the central angle. The sum of the interior angles is (n-2)*180 So, (n-2)180/n is the measure of each interior angle of the polygon. Note that 180(n-2)/n = (180n-360)/n = 180 - 360/n This shows that the central angle is...
March 10, 2017

algebra pleeeease help
#1 triangular pyramid Now, what are your thoughts on the others? Don't expect us to do your whole assignment.
March 10, 2017

Math
well if 1/3 was left, the whole loaf was 3 times as much. So, how many pieces would that be?
March 10, 2017

math
1:20000 = 2.7:54000 54000cm = 0.54km
March 10, 2017

Math
maybe the best choice is the one with the smallest total area -- that is, it uses the least material to make. Or maybe the portion size is such that only one of the containers is a reasonable choice for that amount.
March 10, 2017

Math
Then I guess you need to start studying, eh?
March 10, 2017

Maths
you have something against using actual math symbols, as in 12 1/2% lost: 12.5%, leaving 87.5% spent: .70 * .875 = .6125 left: .375 * 1200 = 450
March 10, 2017

need help zigma mathematics
that's sigma, not zigma. Note that n/(n+1) = 1 - 1/(n+1) So, the sum is the same as n - ? 1/(k+1)! Unfortunately, this cannot be expressed using elementary functions.
March 10, 2017

Math
then you have not read your material. The base is a square of side 9cm, so its area is 9^2 = 81cm^2 Your formula for volume then tells you it is 1/3 * 81 * 4 = 108 cm^3
March 10, 2017

Math
v = 1/3 Bh with B=9^2 and h=4
March 10, 2017

math
5000(1+.09*4)
March 10, 2017

calculus
1st way: figure the weight of a slice of water in the pool. Integrate that weight through a height of its distance from the top. 2nd way: Figure the weight of all the water in the pool. Its center of mass is 5.5 feet from the top of the pool, so lift that weight 5.5 feet.
March 9, 2017

Math
18.31 18.29 or, 18.34901326r7812364781263748126478 18.2500000000000000000000036746237642378
March 9, 2017

Math
month name = input/25 There are, of course, many other possibilities.
March 9, 2017

Math
well, what is the median of a set of numbers?
March 9, 2017

Algebra
multiply exponents and you have 16y^-6 / 25x^-8 = 16/25 x^8 y^-6 = 16x^8 / 25y^6
March 9, 2017

Math
surely you can answer some of this if you draw a diagram. Think about the law of cosines for part 5.
March 9, 2017

Math
the mean is the average age. The median is the central value. Assuming a similar distribution of ages, a higher mean or median will indicate a higher group of numbers.
March 9, 2017

Math
looks like the 2nd group were generally older.
March 9, 2017

calculus
This should clear it up for you... http://math.stackexchange.com/questions/543655/using-hookes-law-to-find-the-work-required-to-stretch-a-spring
March 9, 2017

algebra
so, did you do it?
March 9, 2017

Hope someone has a Question
I think you're being irrational. Was there a question in there somewhere, or do I need some transcedental meditation? And if you have hidden some exponents in there somewhere, try using the caret (^) to designate them, as in x^2 means x squared
March 9, 2017

geometry
Let AD = x The Geometric Mean Theorem states that AD*DB = CD^2 x(20-x) = 25 x = 5(2+?3) Since right triangles ADC and ACB are similar (Angle A is common to both), AC/x = 20/AC AC^2 = 20x = 100(2+?3) AC = 10?(2+?3) = 5(?2+?6)
March 9, 2017

Math
So, the amounts are in the ratio 5:20 = 1:4 Now it's just like the earlier problem. Use their sum.
March 9, 2017

Math
oh please. read your earlier post. 8x=80 x=10 so the numbers are 30 and 50, right? That should have been easy just by inspection.
March 9, 2017

Math - Calculus
I hope it was not you who posted this earlier, where I explained it all. http://www.jiskha.com/display.cgi?id=1489049850
March 9, 2017

Geometry
Note that each value is multiplied by 3.
March 9, 2017

Math
well, yes. The next step is to use their sum to actually find x's value: 8x=80 x=10 Now, you can get the two numbers, once you know x.
March 9, 2017

Math
the numbers are 3x and 5x. so, add them up, solve for x, and ...
March 9, 2017

math
charity: 5% = 15 saves: 2/5 = 40% = 120 remainder: 175 = 55%
March 9, 2017

pre calc
It is not (D) because f(x) has a maximum at 35.12 That means that f(x) fails the horizontal line test on the interval (30.24,40), so it is not invertible there.
March 9, 2017

Science
take just a moment to think about this. Surely you can tell which is the only possible choice. The sun is just a huge, hot ball of gas ...
March 9, 2017

Math
perpendicular lines have slopes whose product is -1. So, you need -k/6 * -3/2 = -1 k = -4 The 2nd line has slope -3/2. So, its angle of inclination is arctan(-3/2) = -56.3°
March 9, 2017

Math Calculus
You know what parabolas look like. (x-1)(x-3) is negative between the roots, so this graph has a bump in the middle. Since the axis of symmetry is x=2, f(-1) = f(5) = 8 f(2) = 1 so, the max value is 8 and the minima are 0. f(2) is also a local max, since it is the vertex of ...
March 9, 2017

Math - extreme values
The critical points are where f' is zero or undefined. It is never undefined. So, remembering your Algebra I, f' = 0 when x=0 or cosx=0: x = odd multiples of ?/2 x=0 is not in the domain, so the only critical points are at x = -?/2 and -3?/2. Naturally, the extreme ...
March 9, 2017

Physics 2017
measure the diameter of the wire. Then, knowing the weight of the coil, and subtracting the weight of the core, the remaining weight is purely the wire. Now divide the mass of wire by the density to get the volume of wire. Divide that by the cross-section area to get the length.
March 9, 2017

science
take a look at Snell's Law
March 8, 2017

math
5C3 if order does not matter
March 8, 2017

Math
20000*1.05^20 - 15000*1.05^20 = (20000-15000)*1.05^20 = 5000 * 1.05^20 or, consider that the difference is just the amount f interest earned by the extra $5000 that Lisa deposited. 5000*1.05^20 Note that the growth factor is 1.05, not just .05, since .05 gets smaller and ...
March 8, 2017

math
(x+2)(x-7) <= 0
March 8, 2017

math
clearly you need roots at -2,1,4 Since p < 0 on the first interval, it must be >0 when x < -2. So, the leading coefficient must be negative, giving us p(x) = -a(x+2)(x-1)(x-4) where a is any positive value. See the graph for a=1 here: http://www.wolframalpha.com/input...
March 8, 2017

Algebra2
my answer is: x^2/9+y^2/4=1 Sorry about that!
March 8, 2017

Algebra2
Write an equation of an ellipse in standard form with center at the origin and with the given vertex and co-vertex vertex at (-3,0) and co-vertex at (0.2)
March 8, 2017

Algebra2
Thank you
March 8, 2017

Algebra2
I forgot my answer: (x+2)^2 = 4(y-5)
March 8, 2017

Algebra2
What is an equation of a parabola with the given vertex and focus? vertex(-2,5) focus(-2,6)
March 8, 2017

Probability: Combinations
6C2 = 6*5/2 = 15
March 8, 2017

Algebra2
Write an equation of a parabola with a vertex at the origin and a directrix at y=-5. my answer is focus 6,0, directrix =-6
March 8, 2017

Algebra2
thank you
March 8, 2017

Algebra2
-3x^2+12y^=84 What are the domain and range My answer domain: all real numbers range: y (less than -) -sqrt7 or sqrt7
March 8, 2017

Algebra2
What are it's line of symmetry? 4x^2+y^2=9 my answer is it has 2 lines of symmetry, the x and y axis
March 8, 2017

maths
If there are e erasers, p pencils, and q pens, we have 2e+4p = 240 6e+p+2q = 395 e+p+4q = 415 If A is the matrix of coefficients, then A^-1 = 1/84 (-2 16 -8) (22 -8 4) (-5 -2 22) Then you have (e p q) = (30 45 85) See here: http://www.wolframalpha.com/input/?i=inverse+%7B%7B2,...
March 8, 2017

Science
No ideas? Surely you have a calculator.
March 8, 2017

Algebra2
thank you
March 8, 2017

Algebra2
4x^2+4y^2=64. what are the domain and range? my answer is domain;all real numbers range;-4<=4<=4
March 8, 2017

Math c2
well, 3?(x^2+1) = ?(9x^2+9) = ?(3x)^2 + 9) So, it looks like a horizontal compression by a factor of 3.
March 8, 2017

Math
well, for usage over 50 therms, the bill for x therms is y = 67.65 + 1.1917(x-50) So, plug in your y values and solve for the x values.
March 8, 2017

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