Wednesday

April 1, 2015

April 1, 2015

Total # Posts: 30,251

**calculus**

u = arcsec(x) x = sec(u) dx = secu tanu du the integrand now becomes u secu tanu du Now use integration by parts and it's a cinch. If still stuck, just google it and I'm sure you can find lots of detailed solutions.
*February 12, 2015*

**computer science**

ok. It's pretty cool, believe me. Oh, yeah -- can't post it here.
*February 12, 2015*

**math**

since the plane is aimed basically SW, but its velocity is basically SE, I'd call it a tail wind, since its southward direction is increased. That's quite a side wind, though, as well. Does the vertical speed matter when considering this?
*February 12, 2015*

**Trigonometry**

the plane flies on a heading, not a bearing. the distance east is 200*sin(90-137) = 200cos(47) = 136.4 km
*February 12, 2015*

**math**

If the expensive side has length x, and the other is y, then the cost is 75x+30*2y = 1750 The area is a = xy Since y = (1750-75x)/60 = (350-15x)/12 a = x(350-15x)/12 = 1/12 (350x-15x^2) This is just a parabola with vertex at x = 35/3. That is x, so now you can figure y.
*February 12, 2015*

**Geometry**

sorry. I get a message saying I have to log in to view the page. Better describe the diagram.
*February 12, 2015*

**Geometric progression**

r = 1/2 try that to get started.
*February 12, 2015*

**statitics**

all probabilities must be positive.
*February 12, 2015*

**math**

Just add up all the powers of 7: 7^[(-1/5)-(-7/5)+(3/5)] = 7^((-1+7+3)/5) = 7^(9/5) The line in question is wrong. 1/7^(-7/5) is NOT 7^(5/7) it is 7^(7/5) 7^(-1/5) is NOT 7^5 it 1/7^(1/5) Reciprocals just cause the exponent to be minus what it was, not the reciprocal. Better ...
*February 11, 2015*

**algebra**

the two candles have height h and h+1 The shorter candle burns at the rate of h/4 in/hr The longer burns at the rate of (h+1)/6 in/hr So, h-(h/4)(2.5) = (h+1) - (h+1)/6 * 4 h = 8
*February 11, 2015*

**physi<u>c</u>s**

aaa
*February 11, 2015*

**algebra**

sorry - 2/3 of 135 = 90, as expected. single is 105/285 = 36.8%
*February 11, 2015*

**algebra**

the population has m men and w women. Assuming that each married person has a single spouse, 2/3 m = 3/5 w So, m = 9/10 w So, assume there are 9 men and 10 women. The given fractions don't give integer results, so we need to multiply the proposed population. LCM(3,5) = 15...
*February 11, 2015*

**geometry**

recall that the length of the altitude is the geometric mean of the two segments of the hypotenuse. That is, w+9 = √(8*18) = 12
*February 11, 2015*

**Algebra 1**

A box shaped like a rectangle prism has a height of 17 inches and a volume of 2,720 in^2. The length is 4 inches greater than twice the width. What is the width of the box?
*February 11, 2015*

**Algebra 1**

Find the solution of x^2+14x+112=0 I don't think that there is a solution
*February 11, 2015*

**Algebra 1**

What is a solution of x^2 +6x=-5? my answer is -1
*February 11, 2015*

**Algebra 1**

What is the value of n so that the expression x^2+11x+n is a perfect square trinomial?
*February 11, 2015*

**Algebra 1**

thank you
*February 11, 2015*

**Algebra 1**

The area of a rectangle is 30 ft^2. The length is 1 less then 3 times the width. How wide is is the rectangle?
*February 11, 2015*

**Algebra 1**

my answer is 42 feet
*February 11, 2015*

**Algebra 1**

A ball is thrown into the air with the in initial upward velocity of 60 ft/s. It's height (h) in feet after t seconds is given by the function h=- -16t^2+60t+6. What will the height be at t=3 seconds?
*February 11, 2015*

**Algebra 1**

my answer is 3 seconds
*February 11, 2015*

**Algebra 1**

A ball is thrown into the air with the in initial upward velocity of 45 ft/s. It's height (h) in feet after t seconds is given by the function h=- -16t^2+45t+6. After about how many seconds will the ball hit the ground?
*February 11, 2015*

**Algebra**

the acceleration is (41m/s)/(.28s) = 146.43 m/s^2 F = ma
*February 11, 2015*

**math**

for the horizontal asymptote, as x gets large, only the highest powers matter. So, what is x^2/9x^2 ? For vertical asymptotes, they can only occur where the denominator is zero. 9x^2-44x-5 = (9x+1)(x-5) so, when is that zero?
*February 11, 2015*

**Icp**

F = ma
*February 11, 2015*

**math**

Seems like you'd have to know the various amounts of debt and interest, doncha think?
*February 11, 2015*

**math**

see the 1st related question below
*February 11, 2015*

**Geometry**

42° = 1/2 (large-small) so, large-small=84° but, large = 7/3 * small 7/3 * small = small+84 4/3 * small = 84 small = 63 large = 147 So, since the three arcs add up to 360°, 63+147+x = 360 x = 150° A nice discussion of the topic is found at http://www....
*February 11, 2015*

**Maths**

Hmmm. Looks like 20 to me, too. There aren't any fractional laps to worry about.
*February 11, 2015*

**Geometry**

Suppose the sides were exactly 3,10,12. The perimeter would be 25. But, the actual perimeter is 400 = 16*25 So, the sides are 16*3,16*10,16*12 = 48,160,192
*February 11, 2015*

**math**

blue beads are 3,6,9,12,15,18 green ones are 7,14 so, what do you think?
*February 11, 2015*

**math**

a = pi r^2 = 38.5 r^2 = 38.5/pi r = 3.50 c = 2pi r = 22.06 Now, for the square: s = 22.06/4 = 5.515 a = 30.42
*February 10, 2015*

**math**

(.05*540 + .80*(720-540))/720 = 23.75%
*February 10, 2015*

**9th Grade Math**

(4πx^2)/(3x^2) = 4π/3 = 4.19
*February 10, 2015*

**math**

2(q^2-3q) = 2q^2-6q So, you want to add up 2q^2-6q+q+10+q^2 Keep like powers together, and you end up with (2+1)q^2 + (=6+1)q + 10 3q^2-5q+10
*February 10, 2015*

**Math**

7/15 - 6/15 = ?
*February 10, 2015*

**Math**

you are correct
*February 10, 2015*

**geometry**

90+62+x = 180
*February 10, 2015*

**vectors**

Looks good to me.
*February 10, 2015*

**Math**

x^6 z^-1/3 / -125 y^-9 z^8/3 = x^6y^9/-125z^3 (x^6y^9/-125z^3)^-1/3 = -5z/x^2y^3
*February 10, 2015*

**messy systems**

n+q = 50 5n+25q = 1030 Now just solve for n and q.
*February 10, 2015*

**Math**

20% of 20 quarts is 4 qt. Adding 5 qt of red will make 9/25 = 36% red
*February 10, 2015*

**math**

If the boys average n points each, then just add up the total points g = 3b 18g + nb = 17(g+b) 54b + nb = 17(3b+b) 54b + nb = 68b 54+n = 68 n = 14
*February 10, 2015*

**Algebra 1**

thank you
*February 10, 2015*

**Algebra 1**

A carpenter is putting a skylight on a roof. If the roof measures 10x +89 by 7x+7 and the skylight measures x+5 by 3x+3, what is the area of the remaining roof after the skylight is built?
*February 10, 2015*

**Algebra 2**

a good long division site is http://calc101.com/webMathematica/long-divide.jsp
*February 10, 2015*

**Algebra 2**

wolframalpha.com is a good graphing site. Just type in your function or equation.
*February 10, 2015*

**calculus**

<mumble>
*February 10, 2015*

**Algebra 1**

A sports team is building a new stadium on a rectangular lot of land. If the lot measures 6x by 10 x and the sports field will be 1x by 4x, how much land will be left over>? My answer is 56x^2
*February 10, 2015*

**Algebra 1**

A garden will be on a rectangle lot 5x by 10x. The garden will be circular with a radius of 3x. How much land will be left over after the garden is built?
*February 10, 2015*

**math**

surely you know how many lb/kg and in/cm. If not, look them up to do the conversions.
*February 10, 2015*

**Math**

because the order or arrangement matters. Otherwise, it'd just be a combination.
*February 10, 2015*

**math**

s = t^3-3t^2-8t+c use s(1) = 10 to find c, then evaluate s(2)
*February 10, 2015*

**Math**

because ((x+10)*4+200)/4-x = 60 for any x
*February 10, 2015*

**Math - eh?**

no idea. You need to provide a little more context. Also a little better grammar.
*February 10, 2015*

**math**

you want arcsin(4/5) in QI and QII, where sine is positive.
*February 10, 2015*

**Math**

The only one I get is 1+2+3-4+5+6+7*8-9 = 60
*February 10, 2015*

**Math**

If there are x at 40 cents, and y at 16 cents, then you know that x = 2y 40x+16y=576
*February 10, 2015*

**Math**

k = 9/2 s s = k-28 Now just solve for k and s and figure k+s
*February 10, 2015*

**algebra**

the slope is (1/2 - 2/5)/(-4/5 - 1/3) = -3/34 So, now you can use the point-slope form to get the equation for the line as y = -3/34 (x - 1/3) + 2/5 You can massage that into the form you want. I assume you can get rid of the fractions.
*February 10, 2015*

**maths please help and explain**

Using somewhat more conventional notation, we have 4((1/2)x+2) = 2((2/3)x-3) 2x+8 = (4/3)x-6 (2/3)x = -14 x = -21 (3x-6)/(2y) = 4 3x-6 = 8y 3x-8y = 6 (2y+3)/4 = 2x 2y+3 = 8x 8x-2y = 3 Doing a little scaling, that's the same as 3x-8y = 6 32x-8y = 12 Now subtract and you ...
*February 10, 2015*

**math**

Clearly, the nth branch produced 2^(n-1) oranges.
*February 10, 2015*

**Trigonometry**

if the height matters, then you need to give some indication of the angles of elevation. Just knowing the direction tells us nothing about the buildings' locations. The N8°W and N10°E are angles measured on the ground. Apparently the 10m is a straight line on the ...
*February 10, 2015*

**Math**

the bedroom is 12*12 = 144 ft^2 the living room is 12*18 = 216 ft^2 so, the bedroom's area is 144/(144+216) of the total. The price of the carpet is irrelevant.
*February 10, 2015*

**math**

5/6 < 1 (5/6)^2 is (5/6)(5/6) < 5/6 so, what do you think?
*February 10, 2015*

**Math**

h(t) = 8t - 2.5t^2 so, just find the vertex of that parabola.
*February 10, 2015*

**Math**

clearly, x=3 and y=2
*February 10, 2015*

**Math**

I get 2x = y+2 2z = x+1 so, t=7
*February 10, 2015*

**Geometry**

well, surely you must recognize that ∠TUS ≅ ∠SUT, so that means that 4x+16 = 2(18x-8) 4x+16 = 36x-16 x = 1 So, ∠SUT = 20° ∠RUS = 10° No idea what ∠RUT is, since you haven't said anything about the relative locations of the points...
*February 10, 2015*

**Pre-Calculus**

oops. wrong vertex. Should be (0,628.0925) y = -0.007015x^2+628.0925
*February 10, 2015*

**Pre-Calculus**

you can do all the graphing stuff. Lots of online places for that. Given the definition of cosh(x), you have the arch as c(x)=693.8597-68.7672(e^0.0100333x+e^-0.0100333x)/2. The vertex of the arch is at c(0) = 693.8597-65.7672 = 828.0925 the arch meets the ground where c(x) = ...
*February 10, 2015*

**math**

If the amounts invested are x,y,z then we have x+y+z = 5000 x+y = z .02x + .03y + .04z = 145 Hmmm. I get -500 for y. Sure there's no typo in the problem?
*February 10, 2015*

**Calculus**

a = ∫[-1,1] y dx
*February 9, 2015*

**Math**

I see six dimensions. That's some room!
*February 9, 2015*

**math**

no idea what you mean when you say you have some numbers "on a prism."
*February 9, 2015*

**Vectprs and Scalars**

if a and b are vectors, a•b is a scalar. a×b is a vector. the dot product • is only defined for two vectors. The cross product × is only defined for two vectors. So, 1,3,5,11 are scalars 6,8,9,10 are vectors 2,4,7,12 are undefined
*February 9, 2015*

**math**

180° is completely straight.
*February 9, 2015*

**Algebra 2**

I have an idea. Why don't you show your work? To start, square both sides, then collect terms and square again. √(2x+1) + √(2x+6) = 5 (2x+1) + 2√(4x^2+14x+12) + (2x+6) = 25 √(4x^2+14x+12) = 9-2x . . .
*February 9, 2015*

**Algebra 2**

x^4-x = 0 x(x^3-1) = 0 x(x-1)(x^2+x+1) = 0 do the other the same way. Factor it out. Each of the factors may be zero.
*February 9, 2015*

**Algebra 2**

enter your function or equation at wolframalpha.com
*February 9, 2015*

**physics**

the range of the ball is R = (v^2 sin2θ)/g so just find v such that (v^2 sin(102°))/9.8 = 14
*February 9, 2015*

**Vb**

well, Integer is misspelled.
*February 9, 2015*

**Math**

1x4 = 4x1 commutative property of multiplication?
*February 9, 2015*

**math**

X and Y are 80° apart. Each time zone is 15° wide. So, the towns are 5 1/3 time zones apart. Depending on their proximity to the zone lines, they could be 6 or 7 hours apart. The rest I'm sure you can do with normal trig operations. If not, show how far you got, so...
*February 9, 2015*

**Math**

7/8 - 5/6 = 21/24 - 20/24 = 1/24
*February 9, 2015*

**Math**

The sum from 1 to n where n is even (2k) is (2^2-1^2) + ... + ((2k)^2-(2k-1)^2) = (2+1)(2-1) + (4+3)(4-3) + ... + (2k+2k-1)(2k-2k+1) = 3+7+...+4k-1 = k/2 (3+4k-1) = k(2k+1)
*February 9, 2015*

**maths**

we want F such that Fx = 3ye^(3x) - 2x Fy = e^(3x) Clearly F = ye^(3x)-x^2
*February 9, 2015*

**algebra**

d = 1.22√(50+5)
*February 9, 2015*

**mathematics**

d/1200 = cot 28°
*February 9, 2015*

**trig - eh?**

Hard to tell, but I am assuming that you meant to say that the taller building is 6/5 as far away as the shorter building. If so, then the shorter building is 5/6 as far away, or 20/3 m. Something tells me the heights matter, but I can't see how, from the data. The ...
*February 9, 2015*

**trig**

Draw a diagram. You will see that the distance d is given using the law of cosines: d^2 = 415^2 + 120^2 - 2*415*120*cos 100°10'
*February 9, 2015*

**maths**

since you have only provided a single value for each coordinate, and the planes are all perpendicular to an axis, the intersection must clearly be (-2,8,5).
*February 9, 2015*

**maths**

there are lots of matrix calculators online. wolframalpha shows that the calculation is http://www.wolframalpha.com/input/?i=solve+{{12%2C4%2C17%2C11}%2C{14%2C8%2C9%2C4}%2C{3%2C7%2C2%2C5}%2C{5%2C12%2C9%2C7}}*{{p}%2C{q}%2C{r}%2C{s}}+%3D+{{5}%2C{8}%2C{12}%2C{7}}
*February 9, 2015*

**math**

1,33 10,42 100,132 5003,5035 I think you need a bit more information.
*February 9, 2015*

**Math**

d/p = 3/4 p-3 = d p = 4d/3, so 4d/3 - 3 = d d/3 = 3 d = 9
*February 9, 2015*

**Math**

f:j = 3:4 j:s = 7:6 LCM(4,7) = 28, so f:j = 21:28 j:s = 28:24 f:j:s = 21:28:24 so, f:s = 21:24 = 7:8 total candy = 54 pieces. You want a box with only 9 pieces. Each box has 18 pieces now. So, just move 9 from one box to another.
*February 9, 2015*

**math**

cos(x) = √3/2 if x = 30° or 330° So, 3θ+120 = 30, 330, 390, 690, ... θ = -30, 70, 90, 190, ... So, pick the values in your domain.
*February 9, 2015*

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