Friday

March 6, 2015

March 6, 2015

Total # Posts: 29,430

**Pre-Calculus**

sequence converges series diverges (unless a=0)
*February 15, 2015*

**Computer Science**

if the original price is $100, the final cost is $91.
*February 15, 2015*

**maths**

#1 for n odd, Tn = 3n-2 For n even, Tn = 1/2^n #2 r^3 = T7/T4 = √81/√3 = √27 r = √3 Now you can find a
*February 15, 2015*

**maths(urgent answer pls)**

n ∑ (2k-1)/[k(k+1)(k+2) = k=1 n(3n+1) -------------- 4(n+1)(n+2)
*February 15, 2015*

**math help**

where is P?
*February 15, 2015*

**Math**

use both equations. e^.04t < 6 for t < 45 http://www.wolframalpha.com/input/?i=plot+15%2Be^%280.04t%29+sin%28pi*t%2F3%29%2C+15%2B6*sin%28pi*t%2F3%29
*February 15, 2015*

**math**

calculate f(2) and f(3) If the value changes sign, then the graph must cross the w axis somewhere in the interval, since f(w) is continuous there.
*February 15, 2015*

**maths**

the area of metal is the area of the small circle plus the area of the sides. The small circle has area 49π Now for the sides. Consider the entire cone with base radius 28 and height 4h. Chop off the top 1/4 of the height, and the missing volume is (1/3)π*7^2*h The ...
*February 15, 2015*

**maths**

h/35 = tan 57°40'
*February 15, 2015*

**mathematics**

Sn = 5/2 n^2 + 7/2 n = n/2 (5n+7) Sn = n/2 (2a+(n-1)d) 5(n-1)+5+7 = 5(n-1)+12 a=6 d=5 T10 = 12+9*5 = 57 check: 6 = 1/2 (12+0) 6+11 = 17 = 2/2 (12+5) 6+11+16 = 33 = 3/2 (12+10) looking good.
*February 15, 2015*

**mathematics**

Better clarify just what 3/5/9 means.
*February 15, 2015*

**mathematics**

ar = a+4 ar^2 = ar+9 r = 9/4 a = 16/5 so, now figure the first 3 terms.
*February 15, 2015*

**math**

the volume of the liquid of height h is v = πr^2*h also, v = (384g)/(0.6g/cm^3) So, equate the two, plug in r, and solve for h.
*February 15, 2015*

**Pre-Algebra**

As always, draw a diagram. Using similar triangles, it is clear to see that 4/5 = (x+4)/15
*February 15, 2015*

**math**

you are apparently using logs base 10, so log 0.096 = log(96*10^-3) = log96 - 3 = log(16*6)-3 = 2log4 + log6 - 3 ...
*February 15, 2015*

**math**

assuming the rectangle is long enough to wrap around the cylinder, a = πr^2 + πr^2 + 2πrh = 2πr(r+h) Now just plug in r and h.
*February 14, 2015*

**Calculus**

y = 3x 3^x - 1 y' = 3*3^x + 3x(ln3)3^x = 3*3^x * (1+x ln3) So, y'=0 when x = -1/ln3 That is the only extremum. Now find whether y" is positive or negative there to determine which kind.
*February 14, 2015*

**math**

An odd question. Since the vectors are independent, they span R^2, and the dimension is 2. Am I missing something here?
*February 14, 2015*

**calc**

does not matter. tan and arctan are inverse functions. tan(arctan(x)) = x As to how to find arctan(3) -- have you no calculator? There are gobs of them online if you do not.
*February 14, 2015*

**Math**

Naturally, that wold be f(w) = 0
*February 14, 2015*

**Math**

best convert to polar form z^4 = 46.87 cis 2.95 so, z = 2.62 cis 0.738 + k*pi/2 for k=0..3 then convert back to rectangular form.
*February 14, 2015*

**Math**

Hmmm. I can see that there could be two solutions -- one in front of the plane of the given points, and another behind it. But since the matrix has a linear determinant, I'm not sure how to get the other one. Need to think on that a bit.
*February 14, 2015*

**Math**

put the coordinates in columns of the matrix M: (2 6 3 x) (2 3 -1 0) (3 0 -1 0) (1 1 1 1) The volume of the tetrahedron is 1/3! |M| = 1/6 (13x-39) So, you want 1/6 (13x-39) = 26 13x-29 = 156 13x = 185 x = 14.23 google tetrahedron vertices volume and you can find several useful...
*February 14, 2015*

**a sond wave is prouduced. 3seconds later its echo**

the sound has to go out and back. SO, how far does sound go in 1.5 seconds?
*February 13, 2015*

**math calculus**

2^x is not the inverse of (1/2)^x log_2(x) is the inverse of 2^x log_1/2(x) is the inverse of (1/2)^x You can check this because if g(x) is the inverse of f(x), f(g(x)) = x and g(f(x)) = x (1/2)^x = 1/2^x they are reciprocals, not inverses.
*February 13, 2015*

**math calculus**

well, (1/2) = 2^-1 go to wolframalpha.com and enter plot y=2^x, y=(1/2)^x
*February 13, 2015*

**math**

do you actually read what I write? I explained k, and I used it. Don't make me do your thinking as well as your math!
*February 13, 2015*

**math**

so, if the dimensions are x and y, 50% increase of y is 1.5y. But, you want the new area to be the same. So, if x is multiplied by k, you want (k)(x)(3/2)(y) = xy (k)(3/2)(xy) = xy k(3/2) = 1 k = 2/3 So, if the new width is 2/3 of the old width, that is a decrease of 1/3, or ...
*February 13, 2015*

**math**

length is 3/2 so, width is 2/3
*February 13, 2015*

**math**

c-15 = (2/9)(c+15) + c/6
*February 13, 2015*

**math**

read what you wrote. There are no numbers given, yet you want a numeric answer? 42 is the answer to the Ultimate Question of Life, the Universe and Everything, so it surely must answer your puny question as well.
*February 13, 2015*

**math**

oh, please. If you divide by 4, the remainder cannot be 8 35 = 8*4 + 3 8 is the quotient 3 is the remainder
*February 13, 2015*

**math**

subtract multiples of 4 till you can't get any smaller. In other words, what is the remainder of 35/4 ?
*February 13, 2015*

**math**

Hmm. yes, good question. However, no rectangle with a diagonal of 20 inches can possibly have an area of 192 square meters!! I fear you have garbled the question.
*February 13, 2015*

**math**

400 is 20^2 looks like you need to review the Pythagorean theorem.
*February 13, 2015*

**math**

xy = 192 x^2+y^2 = 400 Now just find x and y
*February 13, 2015*

**math**

you must multiply everything by 4 to clear the fraction. Why did you continue on with another fraction? And your arithmetic is wrong, as well. 2x + [3x-(4x-5) ]=x/4-2 8x + 4[3x-(4x-5) ] = x-8 8x + 12x - 16x + 20 = x - 8 4x+20 = x-8 3x = -28 x = -28/3
*February 13, 2015*

**math**

OK. Now you show me yours, and I'll show you mine. Just clear the fraction and get rid of the parens. Then it's clear sailing.
*February 13, 2015*

**math**

Huh? I clearly showed the factors of each polynomial. When you divide by a fraction, it is the same as multiplying by its reciprocal. If you can't follow those steps, I fear you have a long road ahead... Sorry about the typo. 7 is near the y on the keyboard. I meant 1 + y...
*February 13, 2015*

**math**

1 + 7/(x+y) = (x+2y)/(x+y) 1 - 3y^2/(x^2-y^2) = (x^2-4y^2)/(x^2-y^2) so, the result is (x+2y)/(x+y) * (x+y)(x-y) / (x-2y)(x+2y) = (x-y)/(x-2y)
*February 13, 2015*

**math**

the only multiples of 6 nearby are 18,24 So, our number might be 16,22 Looks like 16 to me
*February 13, 2015*

**Math Check**

(a) and (b) seem to be ok I don't know what (2) is supposed to be, but that's d^2, not d.
*February 13, 2015*

**math**

well, since 12 is 3/4, 4 is 1/4, right?
*February 13, 2015*

**Algebra 2**

if the horse has speed h, and the motorbike has speed m, then since time = distance/speed, 60/m = 50/h - 2 m = h+10 60/(h+10) = 50/h - 2 60h = 50(h+10) - 2h(h+10) 2h^2 + 30h -500 = 0 Now you can find h, and then m=h+10
*February 13, 2015*

**math**

dS/dt = 3t^2-12t+9 for max/min, find t when dS/dt = 0
*February 13, 2015*

**Math 20-1**

neither. All you have to do is check the difference or ratio between the first two and the 2nd two terms. It is not constant.
*February 13, 2015*

**GEOMETRY**

the ratios given are equal because the angle involved is the same. opposite/hypotenuse is the same.
*February 13, 2015*

**Geometry**

a true b true c false d false (unless you consider r<0 as a reflection as well as a scaling. Then it could be true sometimes)
*February 13, 2015*

**Calculus**

Sorry about my half-angle formula hint. Got me nowhere. Instead, for F(x), let u^2 = 1+sinx 2u du = cosx dx and now you have ∫2u^2 du = 2/3 u^3 = 2/3 (1+sinx)^(3/2) + c Now you can find c, since you know F(0)
*February 13, 2015*

**Pre-Calculus**

You want the sum of the first 8 terms: S8 = a(1-r^8)/(1-r) = a(1-(2/3)^8)/(1/3) = 2.883a So, a = 258/2.883 = 89.49 Your answer is totally unreal. It would have turned 805.4 times in the 1st second, which is way more than the total turns after 8 seconds. I hope that is why you ...
*February 13, 2015*

**Calculus**

your expression is just 1/2 sin(14x) dx
*February 13, 2015*

**Calculus**

f(g(5x))/5
*February 13, 2015*

**maths - ouch!**

Thanks, Reiny. I'm glad someone around here can read!
*February 13, 2015*

**maths**

clearly, d=28 and the sequence is -44, -16, 12, 40, 68, 96, ... hint: 71*28 = 1988 but you didn't start at zero.
*February 13, 2015*

**Calculus**

Try using the half-angle formulas to re-express the integrands.
*February 13, 2015*

**Calculus**

a simple division turns this into ∫sec^2x - secx tanx dx how about that?
*February 12, 2015*

**Geometry**

Apparently PQ is not a bisector. It is just parallel to BC. So, AQ/QC = AP/PB 12/18 = 8/x x = 12
*February 12, 2015*

**mathematics**

since 10*19 = 190 and 10*20 = 200, what do you think?
*February 12, 2015*

**Calculus**

let u^2 = x+1 x = u^2-1 2u du = dx and we have ∫ (u^2-1)/u * 2u du = 2∫u^2-1 du and that's a cinch, right?
*February 12, 2015*

**Geometry B**

Draw a diagram. Using similar triangles, we know that h/9 = 17/√370
*February 12, 2015*

**Math**

or, you can reason that since her speed is 4/3 as great, the time required is 3/4 as much, or 15 minutes.
*February 12, 2015*

**Math**

20 minutes (1/3 hr) at 30 mi/hr is 10 miles. 10mi/(40 mi/hr) = 1/4 hr = 15 minutes
*February 12, 2015*

**Calculus**

the average rate of change of f on [a,b] is just [f(b)-f(a)]/(b-a) f(x) = x^3-x^2+4x+c The c does not matter, so the average rate of change on [-1,4] is just [f(4)-f(-1))/3 = ((64-16+16+c)-(-1-1-4+c))/3 = 70/3 You want a c where f'(c) = 70/3 3c^2-2c+4 = 70/3 c = (1+√...
*February 12, 2015*

**Trigonometry**

This is a trick question. 2√3/5 = 0.69 but sec(x) is never less than 1.
*February 12, 2015*

**Calculus**

oh, please - just expand the square, and divide each term by √x
*February 12, 2015*

**Pre-calculus**

r = ±3
*February 12, 2015*

**Math/Trig**

check the related questions below. Looks like bobpursley did this one already.
*February 12, 2015*

**math**

(3/4)m = (1/2)w m/w = (1/2)/(3/4) = 2/3
*February 12, 2015*

**Science**

look them up in a table of hardness. Easy to find. I can't believe you would post such a question.
*February 12, 2015*

**math**

well, just plug in various values forn: 1(0)-4 = -4 2(1)-4 = -2 and so on...
*February 12, 2015*

**physics**

both are 9*0.7071 since sin = cos = 0.7071 at 45 degrees.
*February 12, 2015*

**Math**

when raising powers to powers, just multiply the exponents. That is because (3^4)^3 = (3^4)(3^4)(3^4) = 3^(4*3) So, you have (y^-5)^-10 = y^50 now multiply that by y^10
*February 12, 2015*

**Math(Asap)**

well, you should have caught my typo. I used 3.5% instead of 3%. Fix it and redo the calculation.
*February 12, 2015*

**Math (Asap)**

#1: 3500(1+.035/2)^(2*20) #2: 92000*0.85^10
*February 12, 2015*

**Algebra 2 - eh?**

umm, how many feet?
*February 12, 2015*

**calculus**

u = arcsin(x) x = sin(u) sqrt(1-x^2) = cos(u) dx = cos(u) du Now you have to integrate cos(u) * u * cos(u) du so integrate by parts.
*February 12, 2015*

**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*

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