Thursday

September 29, 2016
Total # Posts: 44,224

**Math**

If there are n cards, then n is a multiple of 2. so, you want an even number which is 3a+2 or 5b+1 a must be even and b must be odd. 26 = 3*8+2 = 5*5+1 = 2*13

*August 11, 2016*

**Calculus**

yes, those are the two values in the interval [0,2pi)

*August 11, 2016*

**Algebra**

3x5+4-2x2+6-4=15 since the only two odd numbers are the 3x5, and only the product of two odds or the sum of an even and an odd is odd, we must have either 3x(5...) or (3x5)+... see what you can do with that

*August 11, 2016*

**Probability**

well, 19 of the 20 stamps have some blue or red, right?

*August 11, 2016*

**math**

The 1st number is larger than the 2nd: a/b = (5/6):(2/3) = 5/4 So, a = 5/4 b = b * 1.25 so, a is 25% larger than b

*August 10, 2016*

**Sum of geometric sequences**

a=5 r=3 S10 = a(r^10-1)/(r-1) plug and chug

*August 10, 2016*

**Calculus**

better use implicit differentiation: e^(xy) = sinx e^(xy)(y + xy') = cosx x e^(xy) y' = cosx - y e^(xy) y' = (cosx - y e^(xy))/(x e^(xy)) but e^(xy) = sinx, so y' = (cosx - y*sinx)/(x*sinx) y' = (cotx - y)/x or, using logs, e^(xy) = sinx xy = ln(sinx) y + ...

*August 10, 2016*

**Calculus 1**

try using the binomial expansion. You will see that the expression is e^(6/x)^(x/2) + (x/2)e^(6/x)^(x/2-1)(8x) + ... = e^3 + 4x^2*e^3/e^(6/x) + ... where all the rest of the terms ->0 so, the limit is e^3

*August 10, 2016*

**Calculus**

surely you can find the derivative of both top and bottom, no?

*August 10, 2016*

**science**

clearly, that would be 400N/cm^2

*August 10, 2016*

**MATH**

what sentence? All I see is an expression.

*August 10, 2016*

**Geometry**

15 seconds * 5rpm = 5/4 rev So, after 15 seconds, it has rotated 1 1/4 times. I am also having trouble getting the given matrix. How does it rotate? What is the axis of rotation?

*August 10, 2016*

**Chemistry**

since 1mL = 1 cm^3, 16.3 cm^3 * 10.5g/cm^3 = 16.3*10.5 g

*August 10, 2016*

**Chemistry**

use the density of Al to find the volume occupied by 54g g ÷ gm/cm^3 = cm^3

*August 10, 2016*

**Pre-Calc**

There are no intervals involved. since sin(π/4) = 1/√2 the principal value of arcsin, Sin^-1(1/√2) = π/4 But, since there are many other angles, sin^-1(1/√2) = π/4 or 3π/4 and since the period of sin(x) is 2π, sin^-1(1/√2) = &#...

*August 10, 2016*

**Math**

If you mean scale factor, then you multiply whatever dimensions you have by the scale factor.

*August 10, 2016*

**algebra**

12/2 (2a+11d) = 168 a+6d = 7 Now just solve for a and d.

*August 10, 2016*

**Math**

try 500x > 5280 or, x > 5280/500

*August 10, 2016*

**math**

minor sector: a = 1/2 r^2 θ = 1/2 * 25 * π/3 = 25/6 π no idea where A and B are, but angles do not have areas. minor segment: 1/2 r^2 (θ-sinθ) = 1/2 * 25 (π/3 - √3/2) arc length = rθ = 5 * π/3 = 5/3 π I see you found the area ...

*August 10, 2016*

**Maths**

in English, there are no ands in writing large numbers. So, four hundred one thousand eight hundred nine = 401,809

*August 10, 2016*

**History**

thank you

*August 10, 2016*

**History**

Many changes occurred to the a freedman's life during reconstruction. Which of the following freedoms did these individuals gain? 1- right to legalize a marriage and raise a family 2- freedom to choose where to live 3- freedom to establish churches and community centers 4...

*August 10, 2016*

**Math**

compare the unit prices: $5.99/2L = $2.995/L and $2.95/.75L = ? $/L

*August 10, 2016*

**math**

100-(80+85-73) = 8

*August 10, 2016*

**probability statistics**

For A and B, just divide the number of your color by the total. For example, P(blue) = 7/20 D is a trick question.

*August 10, 2016*

**algebra**

ok - what is the cost? did you use an editor?

*August 10, 2016*

**algebra - typo**

what does ^0.3x mean? should there be an x^2 in there somewhere? or just .03x ?

*August 10, 2016*

**math**

Efa started out right, but then lost track of the math. 100% is 10 times 10% So, the full tank is 10 times 30L = 300L

*August 10, 2016*

**physics**

PV=k so, P*8 = 48*15

*August 10, 2016*

**Math**

7 days @ 6 per day is 42 eggs for the week. So, add up the rest and see how many were needed to get to 42.

*August 10, 2016*

**chemistry**

well, you can start off with 2NH3 = N2 + 3H2 now start by changing moles

*August 10, 2016*

**Discrete Mathematics and its Application**

By "truth" do you mean a truth table? If so, just list the 8 rows and the 8 values of the functions, and it is easy to show which are equivalent.

*August 9, 2016*

**Math**

In terms of cm, 57m 50cm = 5750cm 22m = 2200cm The greatest common factor can be found using 5750 = 2 * 5^3 * 23 2200 = 2^3 * 5^2 * 11 So, the GCF is 2*5^2 = 50 Using 50cm stones, the courtyard is 115x44 = 5060 stones

*August 9, 2016*

**math**

huh? None of the above. The total marks for the 10 students is 10*8 = 80 I suspect you have left out something, like the size of the group.

*August 9, 2016*

**Reposting question- Pre-calc**

Excuse me?? Can you not just plug in the x-value? y = 5cot(-2x) so, at x = π/6, y = 5cot(-2 * π/6) = 5cot(-π/3) = -5cot(π/3) = -5/√3

*August 9, 2016*

**Maths**

See the related questions below. A good one is http://www.jiskha.com/display.cgi?id=1353315962 not quite yours, but very close.

*August 9, 2016*

**Mathematics**

In English, I think this reads A parking lot has a capacity of 75 cars. If 3/5 of it is full at one time, how many more cars can be parked? Well, 3/5 of 75 is 45, so what do you think?

*August 9, 2016*

**Maths**

google cylinder inscribed in cone and you will find may expositions of a cylinder inscribed in a cone of base radius R and height h. The only twist to your problem is that you have h and α instead of h and R. If you draw a side view, it its clear that R/h = tan α Now...

*August 9, 2016*

**Math**

e^(.09t) = 2 now solve for t years

*August 9, 2016*

**Math**

5 * 12.3 = 61.5 That is the total of the 5 numbers with that average. So, the missing number is 61.5 minus the sum of the first 4 numbers.

*August 9, 2016*

**math**

497

*August 9, 2016*

**math**

One thousand people stood in a very large circle. Each starting with the Jennifer Lopez look alike, wore a sign on his or her back with a numeral from 1 to 1000 in a clockwise sequence. They began counting off. The Jennifer Lopez look alike said one in and remained in the ...

*August 9, 2016*

**ap chemistry**

(3 mole N)/(1 mole Al(NO3)3) * (.75 mole Al(NO3)3)/L * 0.40L = (0.9 mole N)

*August 9, 2016*

**Science**

(3x)^2 + (5x)^2 - 2(3x)(5x)cos120° = 28 9x^2 + 25x^2 +15x^2 = 28^2 x = 4 So, the two forces are 12 and 20 check: <12,0> + <10,10√3> = <22,10√3> magnitude is 28

*August 9, 2016*

**Mathematics**

If you mean (1+ax)/(1-ax) = p/q q(1+ax) = p(1-ax) q + aqx = p - apx aqx+apx = p-q x(ap+aq) = p-q x = (p-q) / a(p+q)

*August 9, 2016*

**science**

think of a weight w on a horizontal plane (θ=0). All of the force is downward. That means that perpendicular is w*cosθ parallel is w*sinθ As the board is tilted, less and less is perpendicular, and more and more is parallel

*August 9, 2016*

**Statistic**

the possibilities are, of course, 0R 6W 1R 5W 2R 4W So, can you determine how many ways for each of those setups?

*August 8, 2016*

**Calc - help needed**

You did not read the domain carefully, nor did your points meet the requirements. All of your points are in QII and QIV, where tan(x) = -1/√3 The domain is [-3π/2,2π], and all of your points must lie in QI or QIII, where tan(x) > 0 That would mean that the x...

*August 8, 2016*

**Algebra Quadratic Functions**

as usual, the vertex is at s = -b/2a = 3/2 y(3/2) = 25/4 so far, so good. So, when does it hit the ground? When y=0, naturally. So, -s^2+3s+4 = 0 (s+1)(4-s) = 0 so, it hits the ground after 4 seconds.

*August 8, 2016*

**statistics**

Just as the median is the middle point in the range, the 1st quartile is the middle point in the lower half. Your data set is so small that it's hard to divide equally. But, the url below discusses it in some detail. https://en.wikipedia.org/wiki/Quartile

*August 8, 2016*

**math quadratic functions**

If x is one side, let y be the other. Then 4x+4y = 40 x+y = 10 y = 10-x The total area is thus a = x^2+y^2 = x^2 + (10-x)^2 = 2x^2-20x+100 a has a minimum at x = 20/4 = 5 As expected, minimum area occurs when the two squares are in fact equal.

*August 8, 2016*

**Algebra Quadratic EFuncyoon**

the maximum area is at the vertex of the parabola. That is always at the axis of symmetry, x = -b/2a In this case, that is at x = 100/4 = 25 2*25^2 - 100*25 = -1250 ??? Your function cannot be correct, since it is a parabola opening upward, and thus has no maximum. The ...

*August 8, 2016*

**Math**

6n+7p = 2170 If he had x cents left, then 7n+7p = 2170+x+30 6n+8p = 2170+x-50 x = 180 n = 210 p = 130 So, a notebook costs $2.10

*August 8, 2016*

**Calculas**

well, the slope is 3/4 so plug that into the other forms. y = 3/4 x + ? y-k = 3/4 (x-h)

*August 8, 2016*

**Math**

28-6n+7(5n-2)-2n 28-6n+35n-14-2n ...

*August 8, 2016*

**Math**

no, -130-48 = -178 if you think the other way around, the depth started at 130 and then was reduced by 48 as the penguin rose 130-48 = 82 or, as feet from the surface, -130+48 = -82 Get out your number line, and remember that negative means go left, and positive means go right...

*August 8, 2016*

**Math**

-130 + 48 = ?

*August 8, 2016*

**How's that again?**

you want to reword that so it makes sense?

*August 8, 2016*

**Math**

Nope. It's 8^-3, or 1/8^3 B

*August 8, 2016*

**Maths B**

.75m/s * 60s = 45m Draw a diagram. It will show that y cot 30° - y cot 50° = 45

*August 8, 2016*

**Mathematics**

7(x+4) - 2/3 (x-6) < 2(x-3(x + 5)) 7x+28 - 2/3 x + 4 < 2x - 6x - 30 19/3 x + 32 < -4x - 30 31/3 x < -62 x < -6

*August 8, 2016*

**precal**

I assume you mean 2sin2x - 2cosx = 0 4sinx cosx - 2cosx = 0 2cosx(2sinx-1) = 0 so, cosx = 0 or sinx = 1/2 so, there will be four solutions in [0,2π)

*August 8, 2016*

**Physics - eh?**

how can you have a depth of 10 meters per second ???

*August 8, 2016*

**Math**

4x+5x = 6.3 x = 0.7 So, the difference in the two pieces is 5x-4x = x = 0.7

*August 8, 2016*

**Math**

in 6 months, the 92000 will be worth 92000 * (1+.10/12)^6 = 96696.90 lop off 20% of the interest (4696.90) for taxes, he is left with 95757.02 Looks like he'll be better off waiting for the $100K in 6 mo.

*August 8, 2016*

**Math**

500 years is 2 half-lives. So, (1/2)^2 of the original amount will remain

*August 8, 2016*

**physics**

y = ax^2 + bx + c y' = 2ax+b y'(0) = tan60° = √3 so, b = √3 y = ax^2 + √3 x + c y(0) = 5, so y = ax^2 + √3 x + 5 y(60) = 10, so 3600a + 60√3 + 5 = 10 a = (1-12√3)/720 y = (1-12√3)/720 x^2 + √3 x + 5 = -0.027x^2 + 1....

*August 8, 2016*

**math**

1 - 1/12 = 11/12 1/2 * 11/12 = 11/24 3/5 * 11/24 = 11/40 11/40 * 12000 = ?

*August 8, 2016*

**Math**

6eggs/(3hens*4days) * 5hens * 8days = 20eggs

*August 8, 2016*

**mathematics - eh?**

try rewording that so it makes sense, ok?

*August 8, 2016*

**science**

magnet and water

*August 8, 2016*

**Science**

it is reduced by 1/2 each 25 min. 100 min = 4 * 25 so, (1/2)^4 remains

*August 8, 2016*

**Math**

well, just list them: 11 12 21 22

*August 8, 2016*

**math**

2/3 * 1/4

*August 8, 2016*

**IIS math**

how about: add the number of apples in the tree to those on the ground ??

*August 8, 2016*

**Math**

60 minutes for each hour, right?

*August 8, 2016*

**Geometry! Please, HELP!**

90-x = 1/5 (180-x)

*August 7, 2016*

**precalc**

Since v is an eigenvector, Mv = λv so, M^2 v = M Mv = M λv = λ Mv = λ^2 v So, M^n v = λ^n v a ={1,1,1} is an eigenvector because Ma = {4,4,4} = λa where λ=4 So, 4 is the eigenvalue of a If we call the eigenvectors a,b,c, then you can show ...

*August 7, 2016*

**precalc**

there are many eigenvalue calculators online. As for #3, there should be a proof in your text. The discussion about eigenvectors will show that they are a basis for the vector space.

*August 7, 2016*

**Math**

A 5m ladder leaning against a building forms a 30 degree angle with the wall. Find how high it reaches, and how far from the wall its base is.

*August 7, 2016*

**trigonometric**

As always, draw a diagram. If the tree has height h, then (61-h)/44 = tan 36°

*August 7, 2016*

**Calc**

f(x) = x^2+(1000-x)^2 = 2x^2 - 2000x + 1000000 f' = 4x - 2000 f'=0 at x=500 f' < 0 for x < 500, so f is decreasing f' > 0 for x > 500, so f is increasing so, f(1000) > f(998) because f is increasing at that point

*August 7, 2016*

**calculus**

well, you know that cos(x) = 1 - x^2/2! + x^4/4! - ... so, cos(x^2) = 1 - x^4/2! + x^8/4! - ... Now just multiply that by x. See http://www.wolframalpha.com/input/?i=x+cos(x%5E2)

*August 7, 2016*

**Calculus with analytic geometry**

all polynomials have a domain of (-∞,∞) Rational functions do too, except where the denominator is zero. So, f(x) has a domain of (-∞,1)U(1,∞) Near x=1, 2x^2-8 is near -6. So, for x<1 y->∞ x>1 y->-∞ So, f(x) has a range of (-&#...

*August 7, 2016*

**algebra**

is there a question in there somewhere? If you think about it a bit, you probably can figure it out.

*August 7, 2016*

**Math calculus**

v = s^3 dv/dt = 3s^2 ds/dt now just plug in your numbers.

*August 7, 2016*

**Physics**

as usual, rms is peak/√2

*August 7, 2016*

**math**

just subtract 3 from 10.

*August 7, 2016*

**math**

1007544

*August 7, 2016*

**Maths**

see related questions below

*August 7, 2016*

**math**

24P2

*August 7, 2016*

**math**

S5 = a(1-r^5)/(1-r) = 44 S10 = a(1-r^10)/(1-r) = 44 - 11/8 now divide (1-r^10)/(1-r^5) = (44 - 11/8)/44 If that looks tough, note that the numerator is a difference of squares.

*August 7, 2016*

**Maths**

for the dinners, m = 2r adding in the desserts, get the total: m + 11 + r + 11+3 = 75 now just solve for r and add in the $14 for dessert. I suspect a typo, since the answer isn't what I'd expect. Of course, the typo might be mine . . .

*August 6, 2016*

**Maths @MyBad**

As usual, Maestro Reiny had the right of it.

*August 6, 2016*

**Maths**

so, it's a typo. Surely you can fix it and continue with the steps.

*August 6, 2016*

**math**

recall how to find the vertex of a parabola. In this case, that will be at x = -b/2a = 500/0.1 Now use that to find P(x)

*August 6, 2016*

**math**

just add up the interest in the parts. It must equal the whole amount specified. If $x is at 3%, then the rest (9000-x) is at 4%. So, .03x + .04(9000-x) = 320

*August 6, 2016*

**math**

as discussed in Method III here, http://jwilson.coe.uga.edu/emt668/EMAT6680.2000/Lehman/emat6690/trisecttri's/trisect.html your point D will be the centroid of ABC. To find the centroid, read here: http://www.mathopenref.com/coordcentroid.html

*August 6, 2016*