Wednesday

September 2, 2015
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*