Monday

November 30, 2015
Total # Posts: 35,847

**Math**

Looks good to me.
*October 30, 2015*

**math**

type in your functions here and see all the details. http://calc101.com/webMathematica/long-divide.jsp
*October 30, 2015*

**English**

thank you
*October 30, 2015*

**English**

What is the noun clause in the following sentence? I heard that the book is set to release soon.
*October 30, 2015*

**suncrest high school**

reflection in the x-axis takes (x,y) -> (x,-y) so, just change the signs of all the y-values.
*October 30, 2015*

**Maths**

f(x) maps vales in the domain to values in the range, using the given rule. So, to find f(1/4), replace all the x's with 1/4: f(1/4) = 2(1/4)^2 + 2 Now just simplify that.
*October 30, 2015*

**college physics - incomplete**

No unique solution. 20'@90 + 3h@50 = 30+150 = 180km 1h20'@90 + 2h@50 = 120+100 = 220km 2h20'@90 + 1h@50 = 210+50 = 260km Some info is missing.
*October 30, 2015*

**Pre-Algebra, please help!**

only repeating decimals can be expressed as rational numbers. So, you are correct.
*October 30, 2015*

**Trigonometry**

the scale ratio is 3'/8" so, using that ratio on 10", you have 3'/8" * 10" = 3'*(5/4) = 15/4' = 3'9"
*October 30, 2015*

**algebra 1**

Bzzzt. but thanks for playing.
*October 30, 2015*

**algebra 1**

c is slope-intercept. The point slope form of the line through (h,k) with slope m is y-k = m(x-h) any other choices look like that?
*October 30, 2015*

**math**

well, considering that -1 = -3/3, what about -4, -3, -2,...,13 same thing. Just keep adding 1.
*October 30, 2015*

**Math**

that is 0-√3^2 = -√9 = -3 powers come first, then subtraction.
*October 30, 2015*

**Math**

looks like a G.P. with a = 4√3 r = 1/4 S = a/(1-r) = 16/√3
*October 30, 2015*

**Math**

As usual, draw a diagram. You can easily see that if you are x away from the wall, the angle of elevation of the bottom of the screen (A) is cotA = x/3 A = arccot(x/3) angle B to the top is cotB = x/10 B = arccot(x/10) So, since θ = B-A dθ/dt = dB/dt - dA/dt = -3/(x^...
*October 30, 2015*

**Math**

No, you have found cos^2 (x/2) check your half-angle formulas.
*October 30, 2015*

**Algebra**

The domain is the set of all the 1st elements of the pairs. A is the range.
*October 30, 2015*

**math**

old perimeter is 2(w+2w) so, 2(2*w+ 2w+6) = 2(w+2w)+20 Now you can find w and 2w.
*October 30, 2015*

**Calculus 1**

Sorry. I might be less grumpy if you actually showed some of that hard work. Given the info I provided above, (a) B is increasing where B' > 0, so 2/∛ - 1 > 0 2/∛x > 1 2 > ∛x 8 > x So, B is increasing on (0,8) B is decreasing on (-∞,0...
*October 30, 2015*

**Calculus 1**

why is this causing difficulties? B'(x) = 2/∛x - 1 B'(x) = 0 at x=8 as you will recall, B is increasing where B' > 0 B is concave up where B" > 0
*October 30, 2015*

**Calculus 1**

well, the derivative is 7e^-7x where is that zero?
*October 30, 2015*

**Calculus 1**

well, (e^−x)*(−e^−6x) = -e^-7x as you know exponentials have no local max/min, so the extrema are at the ends of the interval. That should pose no difficulty, if you sketch the graph.
*October 30, 2015*

**Math**

well, just keep track of the signs as you work it out. cos2x = 1 - 2sin^2x = 1 - 2*9/25 = 7/25 Or, if you insist on doing it the hard way, cos2x = cos^2x - sin^2x = 16/25 - 9/25 = 7/25 If you came up with -7/25, you need to remember your simple Algebra I!
*October 30, 2015*

**Math**

well, 6/7 of the population has just the symptoms. So, what's 6/7 of 40?
*October 29, 2015*

**math urgent help needed!!**

see the related questions below.
*October 29, 2015*

**math**

gal * miles/gal = miles so, if you know your gas mileage, just do the math.
*October 29, 2015*

**Math Pre-Algebra**

5.55% = 1/18 so, cut the cake into 18 equal squares. The cake is twice as long as it is wide, so that means cut half the cake (6 3/4 x 6 3/4) into 9 pieces, each with a side of 1/3 * 6 3/4 = 2 1/4 inches.
*October 29, 2015*

**math**

They are the points where the graph crosses the x-axis. That is, where ax^2+bx+c = 0
*October 29, 2015*

**precal**

well, the distances are 10(1/3) and 5(7/12) Then just use the Pythagorean Theorem to find the distance.
*October 29, 2015*

**@ Steve or Damon**

well, let's see. Walking an extra 12 steps took an extra 18 seconds. So, the difference in speeds is 3/2 sec/step That means that if we let w = # steps walked s = running rate, sec/step w(s+3/2) + 16s = 60 (w-12)(s+3/2) + 28s = 42 That winds up with w = (120-32s)/(2s+3) ...
*October 29, 2015*

**trigonometry**

1st leg goes (0,2*500) = (0,1000) 2nd leg goes (450sin53°,450cos53°) = (359,271) so, the plane ends up at (359,1271) The distance is thus 1321 @ E74°N
*October 29, 2015*

**math help azap**

well, your only candidates are (1)9 = 9 (3)3 = 9 (9)1 = 9 So, pick 1 or or 3 or 9 for y and see which x values work with it.
*October 29, 2015*

**Math**

ok - now what?
*October 29, 2015*

**mathematics**

b=c+6 b+c=60+8 c = 31
*October 29, 2015*

**English**

In the story "A Contribution to Statistics" 1.) Which of the following words best describes the author's view of humanity? a.) altruistic b.) optimistic c.) pessimistic d.) realistic my answer is a
*October 29, 2015*

**algebra**

23P5
*October 29, 2015*

**algebra**

n=q+6 d=n-2 5n+10d+25q = 270
*October 29, 2015*

**calculus - eh?**

as you have written it, it's not. sec(π) = -1 I think your notation is faulty. I cannot think of any manipulations that end up with that 1/π out front. Is there a derivative or integral involved somehow?
*October 29, 2015*

**algebra**

well, 5/2 = 10/4
*October 29, 2015*

**math**

all correct. good work.
*October 29, 2015*

**math**

xy=630 (x-3)(y+5)=630 You can solve that, or note that 630 = 21*30 = 18*35
*October 29, 2015*

**math**

y=c+5 If chen worked x days, y(x-3) = 180 cx = 180 I get x=12, so yang worked 9 days.
*October 29, 2015*

**maths**

lawn area = 36*15 lawn+path area = (36+2w)(15+2w) So, to find w, just solve (36+2w)(15+2w) - 36*15 = 910
*October 29, 2015*

**math**

U = b (a^2 over x^2 - a over x) or, more readably, U = b(a^2/x^2 - a/x) We can ignore b, since it does not affect where the extrema occur. It's just a scale factor. U = a^2/x^2 - a/x = (a^2-ax)/x^2 = a(a-x)/x^2 clearly the asymptote is at x=0 (asymptotes occur when the ...
*October 29, 2015*

**math**

Let's call the k's a and b just to make things more readable. S = a/x^2 + b/(20-x)^2 If a = 2b, then S = 2b/x^2 + b/(20-x)^2 Now, we can actually ignore b, since it is just a constant multiplier and will not affect where the minimum occurs. So, let's use S = 2/x^2...
*October 29, 2015*

**math**

Your function is correct. Maximum revenue is at x=0. That means that an order for 600 chairs produces the maximum revenue. This would not be the case if the discount were applied only to the excess chairs. Then the revenue would be R(x) = 600*150 + x(150-.25x) Then the maximum...
*October 29, 2015*

**math**

h^2+w^2=30^2 so h = -w+30 what? That's not correct. Now, the strength s is s = wh^2 = w(900-w^2) = 900w-w^3 so, to find the maximum strength, we need ds/dw = 900-3w^2 = 0 This is at w^2 = 300 That means h^2 = 600
*October 29, 2015*

**Pre-calculus**

clearly he means the height of the tower part of the setup. The height h of the tower is found by noting that h = 62tan45° - 62tan38° Just draw a diagram and recall your basic trig functions.
*October 29, 2015*

**Trig application**

just use the law of cosines: x^2 = 459^2 + 288^2 - 2*459*288 cos 10°
*October 29, 2015*

**Math**

If the squares have side x, then the volume is v = x(9-2x)(12-2x) = 4x^3 - 42x^2 + 108x dv/dx = 12x^2 - 84x + 108 = 12(x^2-7x+9) now just find where dv/dx=0
*October 29, 2015*

**AP CALCULUS HELP**

c'mon this is algebra I, after doing the derivatives. Just divide both sides by 2z: dz/dt = (x dx/dt + y dy/dt)/z
*October 28, 2015*

**AP CALCULUS HELP**

dividing by 2, we have zz' = xx'+yy' y' = (zz'-xx')/y not sure where you're going with this
*October 28, 2015*

**Grade 10 Math**

70/x < 1/12 x > 840 cm
*October 28, 2015*

**Geometry**

well, a rectangle has two pairs of equal sides, so AB = CD AD = BC
*October 28, 2015*

**algebra 2 A**

surely you have some ideas on some of the sections?!? A problem like this will not be assigned until after some time has been spent. Whatcha got so far?
*October 28, 2015*

**Algebra 2**

no solution. Absolute value is never negative.
*October 28, 2015*

**math**

5.696 x 10^0
*October 28, 2015*

**math**

well, 200=20*10, so how about 20*11
*October 28, 2015*

**math**

this is a standard measure. 1 section = 640 acres. Or, you can do the math, knowing other standard measures. 1mi^2 = (5280 ft)^2 1acre = 43560 ft^2 now just divide
*October 28, 2015*

**Math**

how long does it take to fall 0.91m? Find that value of t, and use it to find the velocity v = 1.03/t
*October 28, 2015*

**Parametric derivatie help plz**

first, find the slope of the tangent line at any point: dy/dx = (dy/dt)/(dx/dt) Yes, these really are fractions! dy/dx = (3cos3t)/(-2sin2t) Now, at t=pi/2, the point on the curve is (0,-1), and the slope is 0 So, our tangent is the line y+1 = 0(x-0) or y = -1 See the curve at ...
*October 28, 2015*

**geometry**

reflection across the y-axis takes (x,y) -> (-x,y) so, just flip the signs of all the x-values.
*October 28, 2015*

**Calculus**

Check your units. Their answer is in m^3, since it is 4π(20^2)(.02/100)
*October 28, 2015*

**Calculus**

v = 4/3 πr^3 dv = 4πr^2 dr so, plug in your numbers...
*October 28, 2015*

**Math**

Assuming the girls were each going to paint the same number of pots, 60x = 57(x+8) So, find x, and there were 60x pots.
*October 28, 2015*

**math**

(18 3/4)/(3 1/6) = 5 35/38 So, he can make 5 pillowcases, with some cloth left over. 5(3 1/6) = 15 5/6 So, you just need to subtract and you get 18 3/4 - 15 5/6 to find the amount left over.
*October 28, 2015*

**Pre-Calculus**

(1) well, you want 2π/5 t = π/2 and 3π/2 so, that makes t = 5/4 for the first time. Since the period is 2π/(2π/5) = 5, the second time is 5/2 later, at t=15/4 (2) from the period, this occurs at 5/4 + 5/2 k for integer k (3) just solve for t in 21cos((...
*October 28, 2015*

**math**

so, get out your graph paper and plot the points.
*October 28, 2015*

**MATH help**

you have a problem with writing points as pairs of coordinates? A = (-2,6) B = (-5,2) C = (-2,-3) Much easier to read. Now, when you get around to letting us know the rest of the points, maybe you will get some help. General polygonal shapes can always be analyzed by ...
*October 28, 2015*

**precalc**

(1) surely you know that the maximum value of sin() is 1. So, 15+42 is the max for h (2) you want sin (π/7 (t-2)) to be -1, so (π/7 (t-2)) = 3π/2 t=25/2 (3) since the period is 2π/(π/7) = 14, the max will occur at 25/2 + 14k for integer values of k. ...
*October 28, 2015*

**MATH HELP**

except, using function notation, it is f(x) = 4x-6
*October 28, 2015*

**Algebra 2**

hard to make a graph without first devising the function. Had any progress there? Hint: f(0) = 4800 f(x) drops by 600 for each increase in x.
*October 28, 2015*

**Math**

Heck, I can't even figure out what's there. ^ means what? is this supposed to be an equation? A list of numbers doesn't fit into such a scenario. Visit mindreaders.com for help with this one.
*October 28, 2015*

**Algebra**

kind of a sneaky question. The graph of g(x) is f(x)-17, so it is shifted -17 units. But the question explicitly asks how many units down f has been shifted, so the answer is 17.
*October 28, 2015*

**Math**

sinx cosy + cosx siny = sin(x+y) cosx cosy + sinx siny = cos(x-y) using the product-to-sum formulas, sinA cosB = 1/2 (sin(A+B)+sin(A-B)) so, just plug in A = x+y B = x-y
*October 28, 2015*

**Math**

A⊆B is clearly false, since 7 is not an element of B B⊆U is trivially true, since U is the universe containing all sets under analysis.
*October 28, 2015*

**math please help**

no, (-5)/(-5) = 1 so, divide both sides by -5 and you have x = -35/-5 = 7 check: -5*7 = -35 Don't forget your basic arithmetic now that you're doing algebra.
*October 28, 2015*

**math please help**

well, -5/-5 = 1, so ...
*October 28, 2015*

**math help azap**

this is a joke, right? subtract 15 from both sides.
*October 28, 2015*

**Math**

find the angle between the two directions, then use the law of cosines.
*October 28, 2015*

**Algebra**

assuming all the hoses have the same fill rate, 3 hoses fill 5000gal/hr, so that is 5000/3 gal/hr per hose. now you know the hose fill rate, so multiply that by 4, and divide it into 15000gal.
*October 28, 2015*

**maths**

plot the points and then use the usual distance formula.
*October 28, 2015*

**Math**

If the brakes are good enough, they'll never touch. Otherwise, they'll hit at some speed up to 115 mi/hr. and what is an "empack"?
*October 28, 2015*

**Calculus - Differentiate**

just use the quotient rule: y' = (cosx)(x^4) - (sinx)(4x^3) ------------------------------ = (x cosx - 4sinx)/x^5 x^8
*October 28, 2015*

**Math**

Looks good to me.
*October 28, 2015*

**11th grade math**

y^(a-b)
*October 28, 2015*

**San Jose city college**

The upwind speed is 100 mi/hr, and the downwind speed is 120 mi/hr. So, if the plane's speed is p and the wind speed is w (clearly, from the west), p+w = 120 p-w = 100
*October 28, 2015*

**math**

I think you'd be better off with r^4 s
*October 28, 2015*

**alegbra**

It will take x years, where e^(.1175x) = 3
*October 28, 2015*

**Math**

close enough.
*October 28, 2015*

**GOA**

4.9(20/300)^2
*October 28, 2015*

**Maths**

If the digits are t and u, then its value is 10t+u. So, 10t+u = 7u-8 10u+t = 10t+u-9 I don't get an integer solution. Check my interpretation of the text.
*October 28, 2015*

**Algebra**

.4x = 1200 x = 1200/.4
*October 28, 2015*

**calculus**

42.00
*October 28, 2015*

**math**

since the water is already 9 cm deep, another 11 cm must be added. So, the water added is 50*30*11 - 25*25*11
*October 28, 2015*

**math**

72 is the total apples in all 3 baskets. They already listed how many of each kind in the baskets.
*October 28, 2015*

**Math**

log_5(x^2) + 4log_5(x) = 12 2log_5(x) + 4log_5(x) = 12 6log_5(x) = 12 log_5(x) = 2 x = 5^2 = 25
*October 28, 2015*

**Calculus**

y = x^4 dy = 4x^3 dx = 4*1(1/2) = 2 Δy = f(x+Δx)-f(x) = (1+1/2)^4 - 1^4 = 81/16 - 1 = 65/16 = 4.01625 They are nowhere near the same. This is because dx uses a linear approximation (the tangent line at x=1), but the actual graph curves steeply upward. See the graphs ...
*October 28, 2015*

**Math**

well, did you not just plug in the points given? g(1/4) = -9, so -2a+k = -9 g(16) = -6, so 4a+k = -6 a = 1/2 k = -8 g(x) = 1/2 log_2(x) - 8
*October 28, 2015*