Saturday

February 28, 2015

February 28, 2015

Total # Posts: 29,284

**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*

**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*

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