Tuesday

March 31, 2015

March 31, 2015

Total # Posts: 30,212

**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*

**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*

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