Monday
May 30, 2016

Posts by Steve

Total # Posts: 40,886

Mathematics
when you say subtracted by do you mean x-150 or 150-x ? Pick one and set it equal to x/7, then solve for x.
May 18, 2016

math
Assuming you mean that the edge of the cloth is to be trimmed with lace, you want the arc length of the graph. ds^2 = (3cos^2(t)sin(t))^2 + (3sin^2(t)cos(t))^2 dt = 9sin(t)cos(t)(cos(t)+sin(t)) dt integrate that from 0 to pi/2 and multiply that by 4 to get the entire length of...
May 18, 2016

math
4*7
May 18, 2016

math
each term is -2 times the previous one.
May 18, 2016

math
64.1*10^6 / 54*10^4 = 1.19*10^2 = 119 people/mi^2
May 18, 2016

math
start at 8 each term adds 0.5
May 18, 2016

math
B and C are both trinomials. Typo?
May 18, 2016

Math
all the numbers from 1-9 can be formed from the 1st five terms. All multiples of 10 can be formed from the geometric terms (basically just a scaled binary sequence). With that, all the gaps between the tens can be filled with the units.
May 17, 2016

Math (pre-celc 12)
why would you add denominators? These are still just fractions. 1/x = x/(3x+18) multiply by x(3x+18) 3x+18 = x^2 ...
May 17, 2016

ms sue?
.22 + .46 - .10 = .58
May 17, 2016

Algebra 1
The first thing I'd do is multiply by 3 to clear all the fractions: 4s - 9 < 3s + 2 - s 4s - 9 < 2s + 2 2s < 11 s < 11/2
May 17, 2016

integral calculus
∫[0,2] 5x - 5x^2/2 dx
May 17, 2016

calc
3ln2 = ln 2^3 = ln8 by definition, e^lnx = x ln(e^x) = x ln and e^ are inverse functions
May 17, 2016

calc
ln(1/25) = ln(5^-2) = -2 ln(5) e^(3ln2) = e^(ln8) = 8
May 17, 2016

Calculus question ?
nope - just a vertical one
May 17, 2016

word problem math
forget all those decimal points. p+n+d = 9 p+5n+10d = 53 n = d-2 now just solve for p.
May 17, 2016

math
a = kbh a/bh is constant, so you want a such that a/(20*15) = 200/(25*16)
May 17, 2016

Grade 12 Calculus and Vectors
If the dimensions are x and y, then xy = 432, so y = 432/x If the shared side is y, then the cost for our homeowner is c = 2x + y + y/2 = 2x + 3/2 y = 2x + 648/x we want minimum cost, so dc/dx = 2 - 648/x^2 dc/dx = 0 when x = 18 So, the garden is 18x24, with the 24' side ...
May 17, 2016

Algebra II
a 90° clockwise rotation takes (x,y) -> (y,-x) review your rotation matrix definition.
May 17, 2016

Geometry
no idea. what is the relation between the two figures?
May 17, 2016

Math/algebra
what about the formula do you not understand? There are many handy online calculators that you can use to check your answer.
May 17, 2016

maths
2sin(180°+x)sin(90°+x)/cos^4x-sin^4x 2(-sinx)(cosx)/(cos^2x-sin^2x)(cos^2x+sin^2x) -sin2x/cos2x -tan2x
May 17, 2016

math
a = -2 r = -2 T20 = ar^19 = 2^20 = (D)
May 17, 2016

Math
correct
May 17, 2016

Math
the degree is just the highest power of the variable.
May 17, 2016

Math
sounds like the prism is 19x6 by 2 so, there are two bases and two pairs of rectangular lateral faces. It's just a box, and you only have to add up the two areas of the rectangles.
May 17, 2016

Calculus
x+y = 10 p = xy = x(10-x) = 10x-x^2 dp/dx = 10-2x max p at x=5 what a surprise...
May 17, 2016

math
well, is y/x constant? 40/2 is not 20/5 is xy constant? 2*40 is not 5*20 so, neither direct nor inverse. of course, you could have just tried some values in the various choices to check them...
May 17, 2016

Math
not sure what tools you have for estimating polynomial roots, but the signs of the quotient from synthetic division tells you that they are all between -2 and 4. Other than that, some numeric method will have to provide better precision.
May 17, 2016

Algebra
note that each term increases by 5
May 17, 2016

math
if price is p and cost is c, then normally, p = 1.8c If c increases by 20%, then 1.8c - 1.2c = 0.6c that is, the profit has changed from .8c to .6c, or a decrease of 25%.
May 17, 2016

Math
7n-3 = 2n+12 7n = 2n+15 5n = 15 n = 3
May 17, 2016

Science
figure that all the PE has changed to KE
May 17, 2016

math
for a given perimeter, the largest area is enclosed by a square. That is, all 4 sides are equal...
May 17, 2016

Applied calculus
you need Fx = 0 and Fy=0 for a max, so -4x^3 + 2y = 0 -4y^3 + 2x = 0 max f=1/2 at x = y = ±1/√2
May 17, 2016

calculus
z = 1250ln(yx^2)+45(y^2+x)(x^3 -2y)-(xy)^1/2 if x is fixed, dz/dy = 1250/y + 45(2y)(x^3-2y) + 45(y^2+x)(-2) - (1/2)(x)(xy)^(-1/2)
May 17, 2016

calculus
copy/paste font problems garbled the post
May 17, 2016

calculus
well, the distance traveled by the boat is found using d = 280 cot25° - 280 cot 65° speed = distance/time
May 17, 2016

Maths
1/T = 1/60 + 1/30 + 1/15 = 7/60
May 17, 2016

maths
1991 is 4 years from 1987, so the projection is (in billions) 5 * 1.02^4
May 17, 2016

Math
multiply the ratio by 9 and you have 45:18
May 17, 2016

math
using similar triangles, you can see that PH/4 = 18/PH PH^2 = 72 PH^2 + PF^2 = 18^2 PL/4 = PF/PH
May 17, 2016

Percent of loss
523.20 * .192 = ?
May 17, 2016

Geometry
multiply the ratio by 24/5 and you have 72/5 : 24 or 14.4:24
May 16, 2016

science
you are reducing the molarity by a factor of 3, so you need to increase the volume by a factor of 3. 1/3 acid and 2/3 water don't add the acid to the water!
May 16, 2016

Algebra
it lands when h=0. So, just solve the quadratic the way you do normally.
May 16, 2016

science
how long does it take to fall? 4.9t^2 = 30 now use v = 9.8t to get the speed.
May 16, 2016

Physics
it might be, but probably not.
May 16, 2016

math
I suspect a typo. The line from (2,0) to (2,8) is vertical. So, all the other lines must also be vertical or horizontal. They are not. and I think you meant "vertices" of a square...
May 16, 2016

physics
unless you have some idea of the mass of the galaxy, you are stuck. Once you have that, just divide by the sun's mass to see how many "suns" there are in the galaxy.
May 16, 2016

Math
just add up the changes x + 12 + 3 = 44
May 16, 2016

math
well, how many tiles will it take? multiply that by the cost of each tile.
May 16, 2016

maths
start with the sum-to-product formula: sin(√(x+h))-sin(√x) = 2cos((√(x+h)+√x))/2)sin((√(x+h)-√x)/2) or, try substituting u = √x sin(√x) = √x sin(√x) / √x = u * sin(u)/u and you know that lim sin(u)/u = 1
May 16, 2016

Geometry
the distance between those two points is √125 The equation is (x+4)^2 + (y+3)^2 = 125 You have mangled the question somehow. None of the equations has the correct center or radius.
May 16, 2016

maths
Try that again so it makes sense.
May 16, 2016

Mech. Engr./Dynamics/Physics/Math
well, you can start with the observation that the horizontal velocity is constant at v0 * sinθ Now just figure the time needed for each hop, and see if the ball travels enough to skip a step or hit it twice. Of course, you will need to have data on the height and width of...
May 16, 2016

mathematics
if they are the sides of a hexagon, the just add them up.
May 16, 2016

Math
all correct
May 16, 2016

math
7.5" = 10' 10.5" = 14' 10x14 = 140 ft^2
May 16, 2016

Math
review your basic trig functions. Draw a diagram, and you can easily see that cosθ = 1.5/6
May 16, 2016

Pre-Calc College
the fraction left after t minutes is (1/2)^(t/29) so, after two hours (120 minutes), the fraction left is 1/2^(120/29) = 0.0568 To find how log it takes to get to 10mg, 650(1/2)^(t/29) = 10 (1/2)^(t/29) = 1/65 t/29 = log(1/65)/log(1/2) = 6.022 t = 174.65 or, almost 3 hours ...
May 16, 2016

Maths
100000cm = 1km so, the scale is 1cm : 1km that should help
May 16, 2016

math
the integers form an arithmetic sequence, with a = 1 d = 1 So, the sum of the 1st 1000 integers is 1000/2 (2+999) = 500500 This is just an illustration of what Gauss figured out as a kid. You can pair up the numbers starting from the ends 1+1000 2+999 3+998 ... 500+501 There ...
May 16, 2016

math
since they are equal, 2x = 100
May 16, 2016

Trigonometry
Draw a diagram, then take a look at the cot function and you will see that h cot21° - h cot32° = 75
May 16, 2016

math
If their digit's number means the sum of the digits, then there are lots of them. But if since a quotient is only defined for two numbers, that implies that the number is a 2-digit value. I can't think of any two digits whose quotient is 20 and whose sum is 11. I ...
May 16, 2016

Math
x = y-13 x = 3/4 y x=39 y=52
May 16, 2016

Math
4(n-1) = 12 n-1 = 3 ...
May 16, 2016

maths
If one part is 2/7 of the other, then we can divide 54 into 9 parts such that each is 6. Now we see that the two parts are 2*6 = 12 7*6 = 42 12 is 2/7 of 42
May 15, 2016

Integral calculus
As a check, the theorem of Pappus says that the volume is the area times the distance traveled by the centroid, which is 9π*6π = 54π^2.
May 15, 2016

algebra/trigonometry
the easy way is to remember that the sides of a 30-60-90 triangle are in the ratio 1:√3:2 You have a long side of 75, so the other two sides are 75/√3,75,150/√3 The string is the long side. Or, using trig, the length of the string, x, is found using 75/x = ...
May 15, 2016

Math
If we let x = weight of camera y = weight of lock z = weight of crown we have x+y=330 x+z=670 y+z=470 now just solve for x,y,z
May 15, 2016

Algebra
Usually the dependent variable is on the left side. Its valye depends on the expression on the right side. The equation tells how to calculate the result of assigning a value to x.
May 15, 2016

Math
Assuming they paid the tip on the price after discount, then each paid 97.38*0.65*1.18 -------------------- = $18.67        4
May 15, 2016

mathematics
9/9^2 = 15/x^2
May 15, 2016

Maths
m = kn/p^2 now you can find k.
May 15, 2016

Algebra
3 ∑ k^2 k = -1
May 15, 2016

Geometry
atsa right
May 15, 2016

Algebra
note that the numbers grow by 3's. So, the sequence is 3k+ something. 3*1=3, but the first term is 5, so the terms are 3k+2 The sum is thus 4 ∑ 3k+2 k=1
May 15, 2016

math NEED HELP
4^3 * 4^4 / 4^9 = 4^7/4^9 = 1/4^2 or, 4^(3+4-9)
May 15, 2016

Algebra
it is clearly C, because (7x-14) = 7(x-2) but you cannot have a denominator of zero. So, while the fraction is equal to 7 almost everywhere, the value of x=2 is excluded because then the fraction is 7(0)/0 and is undefined. The numerator can be zero whenever it wants, so x=7 ...
May 15, 2016

Algebra
well, A is true, but so is C. So, the answer is D. If you had solved the quadratic you would have found both solutions 7x+84 = -x^2+40x-6
May 15, 2016

Math
44lb * 1kg/2.2lb * 14day * 30mg/(kg-day) = 8400mg
May 15, 2016

maths
give google a try. First hit explores this topic http://mathforum.org/library/drmath/view/56394.html
May 15, 2016

math
1 and 2
May 15, 2016

Pre-Calc
Sure; it's just part of the expression. So, assuming we start with n=1, the powers and denominators go up as 3,5,7,9,... So, the sequence is -x^3/3!, x^5/5!, -x^6/7!, ... though I suspect that maybe we start at n=0. But you can fix it if that's the case.
May 15, 2016

Math
1/8 - 1/9 = 1/72 That's how much of the tank gets filled in one minute with both taps open, right? But the question is poorly worded...
May 15, 2016

Math
4x^2 + x + 9 = 0 the quadratic formula will provide you with the complex roots.
May 15, 2016

Math
use the pythagorean theorem.
May 15, 2016

Math
that is very bogus notation. Try rewriting it with ^ denoting a power, as x^2 = x squared And lose the combined fractions. Use parentheses to delineate the meaning. 2/3/4 might be (2/3)/4 or 2/(3/4) which are not the same.
May 15, 2016

Algebra
C is wrong. Check your +- signs during the expansion
May 15, 2016

Maths
smallest answer will come from subtracting the largest value from the smallest. So, 0 - 7654321
May 15, 2016

Prealgebra
no idea what two-ni means, but the product of 1 2/5 and b is 1 less than 2 1/2 of b can be written as (1 2/5)b = (2 1/2)b - 1 maybe you can take it from there...
May 15, 2016

calculus question ?
You are correct in both cases. Consider f(x) = 1/x and f(x) = tan(x)
May 14, 2016

math
since xy=k, a constant, you need y such that 4y = 8*24
May 14, 2016

Maths
surely you have the formulas necessary. Just plug in your numbers.
May 14, 2016

Geometry
looks good
May 14, 2016

Math
Huh??? The only one of those answers less than 4 hours is A!
May 14, 2016

Math help.
well, plug in -x+13 for y and you get -x+13 = x^2+6x+7 x^2+7x-6 = 0 This has two solutions, but they are not listed among the choices. Check for a typo.
May 14, 2016

Algebra
t^6 + t^3 - 8 = 0 now just use the quadratic formula for t^3: t^3 = (-1±√33)/2 Now you can use de Moivre's formula to get the various cube roots of those two values.
May 14, 2016

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