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Posts by Steve

Total # Posts: 50,491

Algebra
You know the factors will be among (2x+?)(x-?) (2x-?)(x+?) where the ? can be 2,3 or 1,6 Now you just have to play around till you find what works. That 13 in the middle is a good indicator that 1,6 will be involved, since it is so big. Now recall that 13 =12+1, so I expect ...

math
88/9 = 9 7/9

math
Draw a diagram. Label it T = top of pole B = bottom of pole S = tip of shadow In ?SBT, ?S = 8° ?B = 102° So, ?T = 70° Now, using the law of sines, the pole's height, BT can be found using BT/sin8° = 16/sin70° This assumes that the angle of elevation is ...

math
have you tried the law of cosines?

Algebra
Your text above seems to indicate that the last problem was to find the domain of ?(6x-18) You know that square roots of negative numbers are not real, so the radicand must be positive That is, the domain of ?x is x >= 0 So, the domain of ?(6x-18) is 6x-18 >= 0 x >= 3...

Algebra
By this time, you should have been able to find your answers in what was written in the responses.

@Typos ? Us
As you can see from the responses here, if you want a good answer, you need to be clear on just what it is you are asking. It is not our job to figure out what you mean -- it is your job to say it so clearly that you cannot be misunderstood!

Algebra 1
Of course, if you knew how to solve them, you would naturally know how to show your work ... #1 As always, (a+b)^2 = a^2+2ab+b^2 (3?6 + 5?10)^2 = (3?6)^2 + 2(3?6)(5?10) + (5?10)^2 = 54 + 30?60 + 250 = 304 + 60?15 So, (3?6 + 5?10)^2 - 286 + 60?15 = 304+60?15 - 286 + 60?15 = 18...

MATH
writing the ratios as fractions, you have a/b = c/d and c/d = e/f So, transitivity means that a/b = c/d = e/f a/b = e/f

Spanish
I hope a Spanish speaker can help you on this. My Spanish is rudimentary, but even I can tell that there are some serious grammatical errors in this essay.

Maths
oops. I misread. the problem. The above rates are for 1/2 yearly accrual of interest. For annual compounding, the amount is 70000(1+.10)^(3/2) = 80758.28 Actually, though, after a year and a half, the annual rate has only been applied once, so the amount in the account is only...

Maths
compound: 70000(1+.10/2)^3 = 81033.75 simple: 70000(1+(.10/2)*3) = 80500

math
20 - 2(-4)^2

Math
b+g = 1420 3g/4 = b/2 . . .

maths
6:40 = 9:60

Geometry
if EFGH is a square, then there are 4 equal sides. Can you do it now?

Math
clearly, 14 * 1/17

science
Since pressure is N/m^2, the whole elephant would exert (500*10 N)/(4*0.08m^2)

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.

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

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

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

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?

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

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

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

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 ...

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

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

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

geometry
Where are P and Q in relation to K and N?

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.

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

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

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

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

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

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 ...

physics
why do you say it is abnormal?

physics
(70.71i+70.71j)-(0i+100j) = 70.71i-29.29j

calculus
see related problems below.

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

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

Math (Stats)
I agree

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

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.

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...

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

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

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' ...

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

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

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)

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...

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

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

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.

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)

Math
the right one

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?

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

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...

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

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

math
1:20000 = 2.7:54000 54000cm = 0.54km

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.

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

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

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.

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

Math
v = 1/3 Bh with B=9^2 and h=4

math
5000(1+.09*4)

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.

Math
18.31 18.29 or, 18.34901326r7812364781263748126478 18.2500000000000000000000036746237642378

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

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

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

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

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.

Math
looks like the 2nd group were generally older.

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

algebra
so, did you do it?

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

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)

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

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.

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

Geometry
Note that each value is multiplied by 3.

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.

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

math
charity: 5% = 15 saves: 2/5 = 40% = 120 remainder: 175 = 55%

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.

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 ...

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°

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 ...

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 ...

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.

science
take a look at Snell's Law

math
5C3 if order does not matter

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 ...

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