Wednesday
September 2, 2015

Posts by steve


Total # Posts: 33,234

Math
can't see the diagram, but the area of a semi-circle is π/2 r^2 So, the area between two semi-circles of radii r and R is π/2 (R^2-r^2) You have circles of radii 14 and 16. So, plug in your numbers.
June 8, 2015

statistics
there were 15 cards, 5 of them diamonds. So, the chance of getting a diamond is 5/15 After that, having drawn a diamond, there are only 14 cards left, 4 of them diamonds. So, the chance that the 2nd draw is another diamond is 4/14.
June 8, 2015

pre calc
y = kx 9 = 12k, so k = 3/4 y = 3/4 x
June 8, 2015

physics
you have a right triangle, with the hypotenuse = 9 (his actual speed), and one leg=2 (the current) so, his resultant velocity must be upstream at an angle x such that sin(x) = 2/9 and the actual resultant speed s (due north) is √(9^2-2^2) Having gotten his speed s, the ...
June 8, 2015

maths
One subset is {1,3} I expect you meant to ask a little more . . .
June 8, 2015

Calculus
the revenue function is price * quantity, so R(x) = x(50-.01x) profit is revenue less cost, so P(x) = R(x)-C(x) = x(50-.01x) - (10+2x) = -0.01x^2 + 48x - 10 Now just set dP/dx=0 and evaluate P there. Or, just use your Algebra I skills and find the vertex of the parabola.
June 8, 2015

math
d/1400 = 8/450
June 8, 2015

Math
The digits are, as explained above, going right to left, 2 3 4*2=8 2+3=5
June 8, 2015

math
Grrrr! The Greek letter is pi The dessert is pie! Here is the graph. I expect you can use it to help with the other questions. http://www.wolframalpha.com/input/?i=-1800cos%289%CF%80%2F6+t%29%2B1800+for+0+%3C%3D+t+%3C%3D+10
June 8, 2015

science
at deceleration a, the velocity is v = 20-at so t = 20/a the distance traveled by the car is s = 20t + 1/2 at^2 = 20(20/a) - 1/2 a (20/a)^2 = 200/a So, to stop in 50 meters, 200/a = 50 a = 4 m/s^2 check: v = 20-4*5 s = 20*5 - 2*5^2 = 100-50 = 50
June 8, 2015

speed time distance
180 km/hr = 50 m/s the front of the train arrives at t=0. The front of the train leaves the platform at t = 365/50 = 7.3 The back of the train whose length is x leaves the platform at t = 7.3 + x/50 So, solve for x in 7.3 + x/50 = 21
June 8, 2015

math
Neither can I. You never asked a question.
June 8, 2015

math
The volume is x(30-2x)^2 The area is (30-2x)^2 + 4x(30-2x)
June 8, 2015

Math
also recall that cos(x) is negative in QII and QIII
June 7, 2015

Pre-Algebra
direct: y = kx, so k = y/x inverse: xy = k If y varies directly with x, find the constant of variation with x = 4 and y = -24 k = y/x = -24/4 = -6 If y varies inversely with x, find the constant of variation with x=5 and y = 10 k = xy = 5*10 = 50 and do the others in like wise.
June 7, 2015

calc
y is concave up if y" > 0 By the 2nd FT of Calculus, y' = -f(x) = -6/(x+1)^2 y" = 12(x+1)^3 so, where is y" positive?
June 7, 2015

Inequalities
Hmmm. I get (x-3)/(x-2) + 12/(x^2-x-2) > 8/(x+1) (x-3)(x+1) + 12 > 8(x-2) x^2-2x-3+12 > 8x-16 x^2-10x+25 > 0 (x-5)^2 > 0 So, all x except x = 2,5 and -1 Oddly enough, it appears that the real solution is x < -1 or x > 2 and x not 5. See http://www....
June 7, 2015

Math (PLEASE HELP!)
Evidently you do not understand the concept of a range. Your temperature is somewhere in 27±3 24 = 27-3 and 30 is 27+3 So, clearly the range is 24-30
June 7, 2015

math
as usual, maximum area is achieved in a square pen. To show this, note that if the dimensions are x and y, we have 2x+2y=200, so y = 100-x The area a = xy = x(100-x) = 100x-x^2 This is just a parabola, with its vertex at x=50. So, the pen is 50x50, or a square. Hmm. I see I ...
June 7, 2015

Math
you want m where 50 < 15+.10m
June 7, 2015

Math
total socks: 7 so, P(blue,red) = 2/7 * 2/7
June 7, 2015

calc
not sure what you mean by evaluate 4-x and 2x-8 Maybe a look at the graphs will help clarify your thinking: http://www.wolframalpha.com/input/?i=plot+y%3D4-x%2C+y%3D2x-8
June 7, 2015

Walk two moons need help
1st question: have you read it?
June 7, 2015

statistics
1569/23652 = 0.06633 You can do the rounding.
June 7, 2015

statistics
176/232 = 0.75862 You can round that as needed.
June 7, 2015

Statistics
since the yearly salary amounts to 2080*13.50 the benefits amount to 24% of that amount.
June 7, 2015

algebra
y = (10x+7)/(6x+3) now solve for x: (6x+3)y = 10x+7 6xy+3y = 10x+7 (6y-10)x = 7-3y x = (7-3y)/(6y-10) now x is y^-1, so to express f^-1(x), that is f^-1(x) = (7-3x)/(6x-10)
June 7, 2015

Algebra
for the survey, (b) looks better to me for the poems, you have (4/13)(2/12)
June 7, 2015

Algebra
(1.4*8)x10^(1+4) = 11.2x10^5 = 1.12x10^6
June 7, 2015

Math
if the base is x and the height is z, then x^2z = 4 The surface is the base and 4 sides, so a = x^2 + 4xz = x^2 + 4x(4/x^2) = x^2 + 16/x da/dx = 2x - 16/x^2 = (2x^3-16)/x^2 da/dx = 0 when x=2, so the container is 2x2x1
June 6, 2015

Math (PLEASE HELP!)
T = 27±3 |T-27| <= 3 Surely you can figure the range.
June 6, 2015

Math
1/7 = 3/(4x-1) 1 = 21/(4x-1) 4x-1 = 21 4x = 22 x = 11/2
June 6, 2015

Math/Physics
just given arbitrary vectors of some magnitudes, there is no way to compute their sum or difference. Unless you know the x- and y-components, you are stuck.
June 6, 2015

Algebra
x(x+18) <= 175 x^2+18x-175 <= 0 (x+25)(x-7) <= 0 So, -25 <= x <= 7 Or, for real-world tables, 0 <= x <= 7 There is probably a minimum positive width for a useful table.
June 6, 2015

math
The 4th row of Pascal's Triangle is 1 4 6 4 1 That is, (a+b)^4 = a^4 + 4a^3b + 6a^2b^2 + 4ab^3 + b^4 So, (3+b)^4 is 3^4 + 4(3^3)b + 6(3^2)b^2 + 4(3^1)b^3 + b^4 = 81 + 108b + 54b^2 + 12b^3 + b^4 That's all very nice, but if your question is to solve for b in (3+b)^4 = 1...
June 6, 2015

algebra
when you raise to powers, you multiply exponents. Consider: 2^3 = 2*2*2 (2^3)^4 = (2*2*2)*(2*2*2)*(2*2*2)*(2*2*2) = 2^(3+3+3+3) 2^(3*4) = 2^12 So, (x^4 y^5)^5 = x^20 y^25
June 6, 2015

Math
1/4 + 1/s = 1/3 Now just solve for s.
June 6, 2015

algebra
6C3 = (6*5*4)/(3*2*1) = 20
June 6, 2015

math
Draw radii to the points of tangency. Draw a line connecting the centers. Draw a parallel line, 2 units closer to the tangent points. Now you have a right triangle with legs 10 and 6, with the tangent line forming the hypotenuse.
June 6, 2015

math
It won't seem hard after you've done a few dozen of them... I assume you meant 9^(x+2)=240+9^x That is the same as 9^2*9^x = 240 + 9^x 9^x(81-1) = 240 80*9^x = 240 9^x = 3 x = 1/2
June 6, 2015

Math
make that 2n/10 + 5n/7 + 303 = n
June 6, 2015

Math
"several" sevenths? What kind of nonsense is that? Anyway if that means 5/7, then 2/10 + 5n/7 + 303 = n n = 3535
June 6, 2015

math
angle ADB is an exterior angle to triangle ACD. So, it is equal to angles ACD+CAD. Thus angle C is 45 degrees.
June 6, 2015

Math
In the absence of any other information about how the amplitude changes, I'd just use a linear rate of change. For instance, y = (2+0.3x) sin(x) Or, if you insist on a constant amplitude, then averaging them seems like a good option.
June 6, 2015

Math
Assuming even change in height, the rate is 0.5 m/hr So, at what time t do you have 1.4 + 0.5t = 1.71 ??
June 6, 2015

Math
see your original post.
June 6, 2015

math derivatives - eh?
The given information says nothing about the height or width of the building. Without that, we do not know enough to work the problem.
June 6, 2015

Math
see your previous post.
June 6, 2015

Math
come on, man! The common difference is A2-A1 or A3-A2, which they gave you. The difference is shown above: -2p+10 or -3p-13 In either case, it is 56. Now do you think you can write the sequence?
June 6, 2015

Math
since the difference is constant, (5p+12) - (7p+2) = (2p-1) - (5p+12) -2p+10 = -3p-13 p = -23 Now you can find the difference, and write the terms of the sequence.
June 6, 2015

Algebra II
that it is.
June 6, 2015

math
you want, for m miles, 26+.12m = 24+.19m
June 5, 2015

math
a quadratic has x^2 as its highest power. So, A. Note that y decreases by 3 when x increases by 1. So, it will look like y = -3x But, when x=0, -3x=0, and y is -8. So, y = -3x-8 again, A
June 5, 2015

Math- algebra
the colony doubles 4 times every hour. So, after t hours, it has reached 2^(4t) cells. Clearly 4t = 13
June 5, 2015

Geometry
Since triangle DEC is a right triangle, with angle C = 30° and DC=10√3, DE = 10. No idea what the "length" of E is, since it's a point.
June 5, 2015

Math
24/8 = 3 x^4/x^-3 = x^7 z^-2/z = z^-3 Looks like C to me
June 5, 2015

Basic Differential Equation
You have (D^2+16)y = 0 so the solutions are e^(±4ix) or sin and cos (sin 4x)" = -16sin(4x) (cos 4x)" = -16cos(4x) If the answer is just sin(4x) then there must be some other conditions
June 5, 2015

math
you can choose each scoop 5 ways, so 5^3=125
June 5, 2015

Math
multiply by r and you have r^2 = -2rcosø-2rsinø x^2+y^2 = -2x-2y x^2+2x + y^2+2y = 0 (x+1)^2 + (y+1)^2 = 2
June 5, 2015

geometry
4'6" = 54" 9'7" = 115" so the scale is 115/54
June 5, 2015

Algebra help
you want the area of the deck-and-pool to be 832ft^2 greater than just the pool. So, solve for w in (w+8)(3w+8) - 3w^2 = 832 Having gotten w, you can now determine the size of the pool. Sounds to me like the problem is poorly stated. You already know the size of the pool. You ...
June 5, 2015

math
1 3/4 = 7/4 7/4 * 9 = ?
June 5, 2015

math
1 4/5 = 9/5 2/(9/5) * 7 and round up to a whole bottle
June 5, 2015

Math
"larger than" means you subtract, to find the difference. So, you have ((-1)^2 + (-2)^2 + 5^2) - (-1-2+5)
June 5, 2015

Math
Can you factor x^2+x-12? This will be very like that.
June 5, 2015

Math of class-10
∜3 is a root of the equation x^4 - 3 = 0 Using the Rational Root Theorem, any rational roots p/q of that equation must have denominator of 1, and numerator a divisor of 3. Since 3 and 1 are not roots, there are no rational roots.
June 5, 2015

Calculus
Looks like the curve y=e^x on the interval [2,7] rotated around the line x=1. I assume you meant to include dx in the integral. Since the volume of a shell of thickness dx is 2πrh dx, if r = x-1 and h=e^x that fits the bill.
June 5, 2015

Math
(1/2)(3/5) + (1/2)(2/6)
June 5, 2015

algebra
w(2w+2) = 312 Now solve for w.
June 5, 2015

Math
well, geez. Midnight to 10 am is not exactly a full day, now, is it? Most folks are sleeping during most of that period. When you ask "which" it implies that we be given a list to choose from. Maybe we were waiting for you to see that you had not supplied any choices...
June 4, 2015

Math
if sides a and b are equal, then a/sinA = b/sinB means that a/sinA = a/sinB so sinA = sinB Now, A and B need not be equal if their sines are equal, but in that case A = 180°-B and your triangle is just a flat line.
June 4, 2015

math
well, that would be when 20sin 2pi/40 (t-10) + 21 = 15 20sin 2pi/40 (t-10) = -6 sin 2pi/40 (t-10) = -.30 sin .304 = .3, so 2pi/40 (t-10) = pi+.304 or 2pi-.304 t = 31.935 or 48.065 or other values periods away.
June 4, 2015

math
domain is naturally all reals vertical shift is -1, so range is -1-2 to -1+2 amplitude is 2 period is 2pi/3 phase shift is -180
June 4, 2015

Math
First, disambiguate your expression. As it is written, it means (1/6^8)/3 - 2/3 = -3359231/5038848 or do you mean 1/6^(8/3) - 2/3 = 1/∛1679616 - 2/3 or something else entirely? Formatting is not the browser's forte.
June 4, 2015

Math
so she needs a circle of radius 3 (9π) and a rectangle which is 6πx12.
June 4, 2015

Algebra II
Your first step is wrong. Just subtract b². It should be 4b = 3b² 3b² - 4b = 0 b(3b-4) = 0 b=0 or b=4/3 b = -4/3 should immediately be seen not to work, since you have b² + 4b = 4b² If b is negative, there is no way you could subtract something from b&...
June 4, 2015

Trigonometry
Looks good to me. I'd go with the +3cos(2θ + 3π/2)-3 since the cosine function is what is being given, not a flipped or shifted cosine.
June 4, 2015

math
looks like you're all set to use the distance formula. So plug in your numbers, as you have declined to share them with us.
June 4, 2015

Computers
I score it 2+4+0+3+2=11/20
June 4, 2015

Applications: Percents
After n years, the interest is prn. So, you want (20500)(.06)n = 5535 n = 4.5 years To double, you need .06n=2, or n=33.3 years
June 4, 2015

Find the GCF of the monomials
3x is the largest factor that divides all three monomials. So, it is the GCF. Trent: Since the terms have not been added, there is no sense in trying to factor it. In any event, assuming such a sum would have yielded 3x(y+2z+3yz)
June 4, 2015

Chem.
pressure has increased by a factor of 1.165/0.973 = 1.197 1.197 * 0.250 = 0.299 So, 0.049 mols were added. (Probably 0.05)
June 4, 2015

Chemistry
22.4 Mol/L at STP means 44.8 moles of H2 Each mole of Zn produces one mole of H2, so you need 44.8 moles of Zn. How many grams is that?
June 4, 2015

math help
quadratic sequences will have linear 1st differences and constant 2nd differences. The 1st differences here are 5,x-9,37-x The 2nd differences are x-14,46-2x If x=20, that makes the 1sts: 5,11,17 and the 2nds 6,6 which is consistent. I expect you can determine the nth term all...
June 4, 2015

math
ax^2+bx=bx^2+a (a-b)x^2 + bx - a = 0 The discriminant is b^2 + 4a(a-b) = b^2-4ab+4a^2 = (b-2a)^2 since that is a perfect square, plugging it into the quadratic formula will always yield a rational result if a and b are rational. Note that the question is invalid if a or b is ...
June 4, 2015

Math
So, lay out the jeans in a row. There are 5 pairs. Pick the first one. There are 5 ways to do it, right? That leaves 4 pairs to choose the other one you want. There are 4 ways to pick that one. So, for each of your first 5 choices, you have 4 other choices, making 5*4 = 20 ...
June 4, 2015

math help
Assuming you mean 3^x = 81 - 3^x 2*3^x = 3^4 log32 + x = 4 x = 4 - log32 Somehow I suspect a typo.
June 4, 2015

math
since sec^2 = 1+tan^2, you have 2+2tan^2 + tan^2-3 = 0 3tan^2 = 3 tan^2 = 1 tan = ±1 now, where is that true?
June 4, 2015

math
x^2+4y^2+6x-8y+9=0 x^2+6x + 4y^2-8y = -9 x^2+6x+9 + 4y^2-8y+4 = -9+9+4 (x+3)^2 + 4(y-1)^2 = 4 (x+3)^2/4 + (y-1)^1 = 1 Now the rest should be easy. Come on back if you get stuck.
June 4, 2015

Math
as always (a) draw a diagram (b) review your basic trig functions Then it will be clear that tanθ = 300/50
June 4, 2015

math
2x^2-2x-24 2(x^2-x-12) 2(x-4)(x+3)
June 4, 2015

math
suppose you had f(x) = 4-x^2 The roots would be x = ±2 4-(x+1)^2 is the same graph, just shifted left by 1, so its roots are x = -1±2 = -3,1 See http://www.wolframalpha.com/input/?i=-%28x%2B1%29^2%2B4
June 4, 2015

Math: Arithmetic Sequence.
a3 and a16 are 13 terms apart. So, 13d = 47-8 = 39 d=3 a+2d=8, so a=2 Now you know a and d.
June 4, 2015

maths
Hmm. I was looking for a cute way, but I guess I'll just have to brute-force it. secx + tanx = m secx(1+sinx) = m 1+sinx = m cosx (1+sinx)^2 = m^2 cos^2 x sin^2 + 2sin + 1 = m^2 - m^2 sin^2 (1+m^2)sin^2 + 2sin + 1 = 0 now solve that using the quadratic formula. Because of ...
June 4, 2015

geometry
you know by now that the standard equation for a circle with center at (h,k) and radius r is (x-h)^2 + (y-k)^2 = r^2 So, just plug in the numbers above. And see your other posting for a similar answer.
June 4, 2015

maths
first step: arrange terms in descending power 8s^2+14s-14 = 0 now you can divide by 2 just to use smaller numbners: 4s^2+7s-7 = 0 Now use the quadratic formula: s = (-7±√161)/8
June 4, 2015

math
a = 12/b^4, so (12/b^4)^5 b^5 = 7776 12^5/b^15 = 7776 b^15 = 32 b = ∛2 so, a=12/∛16 = 6/∛2
June 4, 2015

C programming
usually arrays are declared with type name[]; or type name[n]; or type* name;
June 3, 2015

Science
acceleration from gravity of any object on earth is -9.81 m/s^2 Is there more to this question?
June 3, 2015

physics
s = v^2/2a solve that for a, and the F=ma.
June 3, 2015

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